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OF   THE 

UNIVERSITY  OF  CALIFORNIA. 


Class 


EXAMINATION  OF  WATER. 


LEFf MANN. 


BY  THE  SAME  AUTHOR. 


Sanitary  Relations  of  the  Coal-tar  Colors. 

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EXAMINATION  OF  WATER 


FOR 


SANITARY  AND  TECHNIC  PURPOSES, 


BY 

HENRY  LEFFMANN,  A.M.,  M.D.,  PH.D., 

PROFESSOR   OF    CHEMISTRY  IN   THE  WOMAN'S  MEDICAL  COLLEGE  OF  PENNSYL- 
VANIA AND  IN  THE  WAGNER  FREE  INSTITUTE  OF  SCIENCE;    PRESIDENT 
OF    THE    ENGINEERS'    CLUB    OF    PHILADELPHIA    1901 ;     VICE- 
PRESIDENT  (BRITISH)  SOCIETY  OF  PUBLIC   ANALYSTS 
1901-02  ;  CHEMIST  STATE  BOARD  OF  HEALTH 
OF  PA.  (EASTERN    DISTRICT.) 


FIFTH  EDITION,  REVISED  AND  ENLARGED,   WITH 
ILLUSTRA  TIONS. 


OF  THE 

DIVERSITY  } 

OF 


PHILADELPHIA 
P.  BLAKISTON'S   SON   &    CO. 

1012     WALNUT     STREET 
1904 


COPYRIGHT,  1903,  BY  P.   BLAKISTON'S  SON  &  Co. 


PRESS  OF 

WM.    F.    FELL  COMPi 
PHILADELPHIA 


I    DEDICATE   THIS    BOOK    TO   THE 
MEMORY    OF 

/ID$  fl&otber, 

TO   WHOSE  WISE    PRECEPT    AND    EXAMPLE 

/ 
IN    MY    BABYHOOD 

I    OWE   WHATEVER    MERIT    MY    MANHOOD    YEARS 
MAY   SHOW. 


1 63458 


— If  thou  couldst,  doctor,  cast 
The  water  of  my  land. 


PREFACE. 


IrTthe  present  edition,  numerous  revisions  have  been 
made  but  the  plan  of  the  book  has  not  been  disturbed.  In 
the  four  editions  which  have  been  issued,  it  has  seen  notable 
changes  in  the  attitude  of  experts  toward  certain  methods. 
When  the  first  edition  was  issued,  under  the  joint  author- 
ship of  Dr.  William  Beam  and  myself,  bacteriologists  were 
enthusiastically  claiming  to  be  able  to  determine  absolutely 
the  presence  or  absence  of  disease-producing  microbes  in 
water,  and  asserting  that  sanitary  analysis  of  water  by  chem- 
ical methods  was  about  to  become  a  matter  of  history.  At 
present,  the  limitations  of  bacteriology  are  evident,  and  the 
value  of  routine  chemical  analysis  is  generally  recognized. 
Upon  this  point,  and  also  on  the  question  of  the  inherent 
danger  of  unfiltered  surface  water  even  when  not  receiving 
sewage  directly,  the  book  took  decided  stand,  and  the  devel- 
opment of  the  views  of  experts  has  fully  justified  it.  Long 
experience  has  convinced  me  that  for  determining  the  pota- 
bility of  water,  the  determinations  of  chlorin,  nitrates  and 
nitrites  afford  the  most  satisfactory  indications,  and  that  the 


X  PREFACE. 

figures  for  nitrogen  or  ammonium  (so-called  "free  am- 
monia") and  nitrogen  by  permanganate  (so-called  "albu- 
minoid ammonia")  are  of  much  less  value  than  is  generally 
supposed.  The  suggestion  of  Woodman,  that  phosphates 
afford  a  useful  datum,  is  worthy  of  special  attention. 

ng  South  Fourth  Street, 

Philadelphia,  November,  1903. 


CONTENTS. 


NOTE  ON  WATER-SUPPLY, 


NATURAL  HISTORY  AND  CLASSIFICATION  OF  NATURAL  WATERS. 
Rain    Water  —  Surface    Water  —  Subsoil    Water  — 

Deep  Water,  _______________________________     16-21 

ANALYTIC  OPERATIONS. 

Sanitary  Examinations: 

Collection  and  Preliminary  Examination  —  Total 
Solids  —  Chlorin  —  Nitrogen  in  Ammonium  Com- 
pounds and  Organic  Matter  —  Nitrogen  as  Ni- 
trates —  Nitrogen  as  Nitrites  —  Oxygen-consuming 
Power  —  Phosphates  —  Dissolved  Oxygen  —  Pois- 
onous Metals  —  Biologic  Examinations,  _________  22-87 

Technic  Examinations: 

General  Quantitative  Analysis  —  Spectroscopic  An- 

alysis —  Specific  Gravity,  _____________________  87-105 

INTERPRETATION  OF  RESULTS. 

Statement  of  Analysis  —  Sanitary  Applications  — 
Action  of  Water  on  Lead  —  Technic  Applica- 
tions —  Boiler  Waters  —  Sewage  Effluents  —  Puri- 
fication of  Water  —  Identification  of  Source  of 
Water,  ____________________________________  106-135 

ANALYTIC  DATA. 

Factors  for  Calculation  —  Conversion  Table,  -------  136-137 

INDEX. 


XI 


OF  THE 

UNIVERSITY 

OF 


NOTE  ON  WATER-SUPPLY. 

The  human  race  must  have  recognized  at  an  early  period 
the  value  of  an  abundant  supply  of  pure  and  refreshing 
water.  Pastoral  communities  would  be  obliged  to  guide 
their  movements  along  lines  that  would  keep  them  within 
convenient  reach  of  streams  and  pools  for  watering  cattle; 
agricultural  nations  could  only  establish  themselves  where 
water  was  abundant.  Of  the  two  classes,  the  former  would 
be  much  less  likely  to  develop  soil-pollution,  and,  accord- 
ingly, we  find  that  it  is  with  agricultural  and  manufac- 
turing centers — i.  e.,  towns  and  cities — that  the  serious 
difficulties  with  regard  to  water-supply  arise.  Drainage 
areas  are  easily  polluted;  in  all  the  civilized  countries  the 
streams  receive  more  or  less  sewage,  and  are  correspond- 
ingly offensive  to  the  senses  and  dangerous  to  health. 
The  subsoil  is  better  adapted  to  deal  with  normal  pollu- 
tion, but  its  powers  are  not  inexhaustible,  and  in  time 
wells  and  springs  become  unsafe.  The  usual  course  of 
events  in  this  matter  is  well  portrayed  by  Sextus  Julius 
Frontinus,  who  was  Water  Commissioner  of  Rome  from 
A.  D.  97  to  103,  and  who  has  left  us  a  comprehensive  ac- 
count of  the  water-supply  of  that  city.  He  says  that  from 
the  building  of  the  city  until  its  four  hundred  and  forty- 
first  year  (312  B.  c.),  the  citizens  were  supplied  with  water 
from  the  Tiber,  or  from  wells  and  springs.  These  springs, 
as  with  other  nations  of  antiquity,  were  often  credited 


14  NOTE    ON   WATEK -SUPPLY. 

with  healing  powers,  either  due  to  some  medicinal  in- 
gredients or  because  the  locality  was  supposed  to  be  the 
abode  of  a  minor  deity,  whose  favor  could  be  secured 
in  various  ways.  The  Roman  water-supply  became 
unsatisfactory;  aqueducts  were  built,  and  these  supplied 
the  city  for  centuries.  Two  of  the  original  aqueducts 
are  still  in  use,  supplying  modern  Rome  with  excellent 
water.  The  quantity  of  water  supplied  to  the  ancient 
city  during  the  height  of  the  development  of  the  aqueduct 
system — the  early  part  of  the  second  century  of  the  Chris- 
tian era — is  not  accurately  known,  but  Clemens  Herschel, 
after  careful  examination  of  all  data,  fixes  it  at  about  50,- 
000,000  gallons  a  day.  Most  of  the  supply  was  of  good 
quality,  but  some  of  the  aqueducts  delivered  river  water 
that  was  frequently  turbid.  No  proper  filtering  basins 
were  in  vise,  but  special  interrupting  chambers  assisted 
in  getting  rid  of  the  coarser  suspended  matters. 

Much  less  is  known  of  the  water-supply  of  the  other 
great  cities  of  the  ancient  world.  Aristotle,  in  his  "Con- 
stitution of  Athens,"  refers  to  an  official  designated  "  Super- 
intendent of  Springs,"  which  shows  that  municipal  hygiene 
was  not  wholly  overlooked  in  that  city.  Jerusalem,  during 
its  influential  period,  was  apparently  well  supplied  with 
water.  The  remains  of  underground  conduits  have  been 
lately  discovered,  including  a  tunnel  cut  through  rock 
to  a  point  distant  about  300  meters  in  a  direct  line,  but 
an  actual  length  much  greater  on  account  of  the  tortu- 
ous course.  This  tunnel  was  probably  executed  in  the 
reign  of  Hezekiah  (eighth  century  B.  c.).  An  inscription 
found  on  the  interior  wall  some  years  ago,  states  that  the 
tunnel  was  bored  from  each  end  and  the  borers  met  nearly 


NOTE   ON   WATER-SUPPLY.  15 

in  line.  It  leads  from  a  spring,  now  called  the  Virgin's 
Spring  (considered  as  identical  with  the  ancient  Gihon), 
to  a  point  near  the  Pool  of  Siloam,  at  the  southeast  corner 
of  the  city. 

In  common  with  the  general  decline  of  intelligence  and 
morals  which  affected  Europe  during  the  thousand  years 
from  the  fifth  to  the  fifteenth  century,  the  protection  of 
the  water-supply  was  but  little  regarded.  The  aqueducts 
of  Rome,  Athens,  and  Lyon  fell  into  disuse,  and  ev.en  at 
present  are  mostly  represented  by  a  few  scattered  ruins 
studied  only  by  the  antiquary  and  historian. 

It  is  not  appropriate  to  discuss  the  engineering  features 
of  ancient  or  modern  water-supply,  but  it  is  worth  while 
to  correct  a  wide-spread  error  in  regard  to  the  Roman 
engineers.  It  is  often  said  that  they  did  not  know  that 
water  will  rise  to  its  original  level,  and,  therefore,  built 
extensive  aqueducts  to  carry  water  over  valleys.  The  fact 
is  that  they  were  as  fully  aware  of  the  principle  as  modern 
engineers,  but  it  was  usually  cheaper  for  them  to  build  the 
aqueducts  than  to  use  inverted  siphons.  They  did  use  the 
latter  at  times.  In  the  first  century  of  the  Christian  era, 
an  aqueduct  for  supplying  Lyon  (Lugdunum)  was  pro- 
vided with  a  series  of  seven  lead  pipes,  each  about  20  cen- 
timeters in  diameter,  to  carry  water  across  a  deep  valley. 


NATURAL  HISTORY  AND  CLASSIFICATION  OF 
WATER. 

Pure  water  is  an  artificial  product.  Natural  waters 
always  contain  foreign  matters  in  solution  and  suspension, 
varying  from  mere  traces  to  very  large  proportions.  The 
properties,  effects,  and  uses  of  water  are  considerably 
modified  by  these  ingredients,  and  the  object  of  analysis  is 
to  ascertain  their  character  and  amount.  Since  these  are 
largely  dependent  on  the  history  of  the  water,  a  classifica- 
tion based  on  this  will  be  convenient.  We  may  distinguish 
four  classes  of  natural  waters : 

Rain  Water. — Water  precipitated  from  the  atmosphere 
under  any  conditions,  and  therefore  including  dew,  frost, 
snow,  and  hail. 

Surjace  Water. — All  collections  of  water  in  free  contact 
with  the  atmosphere,  as  in  streams,  seas,  lakes,  or  ponds. 

Subsoil  or  Ground  Water. — Water  not  in  free  contact 
with  the  atmosphere,  percolating  or  flowing  through  soil 
or  rock  at  moderate  distance  below  the  surface,  and  de- 
rived in  large  part  from  the  rain  or  surface  water  of  the 
district. 

Deep  or  Artesian  Water. — Water  accumulated  at  con- 
siderable depth  below  the  surface,  from  which  the  subsoil 
water  of  the  district  has  been  excluded  by  difficultly  per- 
meable strata. 

Rain  water,  when  gathered  in  the  open  country  and 
in  the  later  period  of  a  prolonged  rain  or  snow,  is  the  purest 

16 


SURFACE   WATER.  17 

form  of  natural  water.  When  collected  directly,  it  con- 
tains but  little  solid  matter,  this  consisting  principally  of 
ammonium  compounds  and  particles  of  organic  matter, 
living  and  dead,  gathered  from  the  atmosphere.  In  dis- 
tricts near  the  sea  an  appreciable  amount  of  chlorids  will 
be  present.  It  is  obvious  that  a  prolonged  rain  will  wash 
out  the  air,  but  since  storms  are  usually  attended  by  wind, 
fresh  portions  of  air  are  continually  flowing  in,  and  thus 
the  water  never  becomes  perfectly  pure.  Rain  water 
collected  in  inhabited  districts  is  usually  quite  impure. 

Surface  Water.— Rain  water  in  part  flows  off  on  the 
surface,  and  gains  in  the  proportion  of  suspended  and  dis- 
solved matters,  the  former  being  found  in  large  amount 
when  the  rainfall  is  profuse.  The  wearing  action  of  water 
is  dependent  on  the  amount 'and  character  of  these  sus- 
pended materials.  From  th,e  higher  levels  of  a  watershed, 
the  streams,  more  or  less  in  the  form  of  torrents,  gather 
into  larger  currents,  and,  reaching  lower  levels,  become 
slower  in  movement,  and  deposit  much  of  the  suspended 
matter.  By  admixture  of  the  waters  from  widely  separated 
districts  the  character  and  amount  of  the  dissolved  matters 
are  much  modified. 

It  is  obviously  impossible  to  establish  close  standards  of 
composition  for  surface  waters.  In  the  case  of  rain  water, 
falling  on  the  surface  of  undisturbed,  unpopulated  terri- 
tory, the  amount  of  solids  dissolved  will  be  small,  and 
will  consist  principally  of  carbonates  and  sulfates.  The 
water  of  lakes  and  rivers  is,  however,  in  part  derived  from 
springs,  which  may  proceed  from  great  depths,  and  thus 
introduce  substances  not  easily  soluble  in  surface  water, 
nor  derivable  from  the  soil  of  the  district. 


1 8  HISTORY  AND   CLASSIFICATION. 

The  exposure  to  light  and  air  which  surface  water  under- 
goes, results  in  the  absorption  of  oxygen  and  loss  of  car- 
bonic acid,  together  with  the  oxidation  of  the  organic 
matter.  The  diminution  of  the  rapidity  of  the  current 
permits  the  deposition  of  the  suspended  matters,  and  this 
occurs  especially  as  the  river  approaches  the  sea,  not  only 
from  the  retarding  influence  of  the  tidal  wave,  but  from 
the  precipitating  action  of  the  salt  water. 

Subsoil  Water. — Water  that  penetrates  the  soil  passes 
to  various  depths,  according 'to  the  porosity  and  arrange- 
ment of  the  strata.  As  a  rule,  it  descends  until  it  reaches 
but  slightly  pervious  formations,  upon  the  level  of  which 
it  accumulates.  In  the  upper  layer  of  soil  it  dissolves 
mineral  and  organic  ingredients,  and  becomes  impreg- 
nated with  microorganisms,  through  the  agency  of  which 
the  organic  matter  undergoes  important  transformations. 
The  water,  constantly  accumulating,  gradually  flows 
along  the  incline  of  the  impervious  stratum,  or  through  its 
fissures,  and  may  either  pass  downward  or  emerge  in  the 
form  of  a  spring. 

Much  difference  is  observed  in  the  composition  of  sub- 
soil waters,  but  as  a  general  rule  they  contain  small  amounts 
of  mineral  substances  and  organic  matter.  In  popu- 
lated districts,  however,  a  marked  change  is  produced 
through  admixture  with  water  containing  animal  and 
vegetable  products  in  various  stages  of  decomposition. 
It  is  especially  the  organic  matter  containing  nitrogen 
that  is  of  importance.  These  are  mostly  unstable,  and 
decompose,  partly  by  oxidation,  partly  by  splitting  up 
into  simpler  forms;  changes  in  most  cases  brought  about 
by  microorganisms.  The  nitrogen  is  in  part  converted 


DEEP   WATER.  19 

into  ammonium  compounds,  but  a  considerable  portion 
suffers  further  oxidation,  and  in  association  with  the 
mineral  substances  present  forms  nitrites  and  nitrates, 
especially  the  latter.  This  is  called  "nitrification." 

Nitrification  takes  place  under  the  influence  of  microbes, 
the  habitat  of  which  does  not  extend  more  than  a  few 
yards  below  the  surface  of  the  soil.  Several  microorganisms 
with  active  nitrifying  powers  have  been  isolated  and  de- 
scribed. The  nitrifying  action  is  often  exerted  upon  the 
ammonium  compounds  formed  from  the  organic  matter. 
The  presence  of  some  substance  capable  of  neutralizing 
acids  is  usually  necessary  to  continuous  action.  Calcium 
and  magnesium  carbonates  fulfil  this  function.  Nitrates 
are  the  final  result  of  this  action;  nitrites  are  present  at 
any  given  time  only  in  small  quantity.  Denitrification— 
that  is,  the  reduction  of  nitrates  and  nitrites  to  ammonium 
compounds — takes  place  also  under  the  influence  of  mi- 
crobes, and  is  especially  apt  to  occur  when  considerable 
quantities  of  decomposing  organic  matter  are  introduced. 
Several  species  of  denitrifying  bacilli  have  been  described. 
A  partial  reduction  sometimes  occurs,  and  a  notable  pro- 
portion of  nitrites  is  found,  but  in  the  presence  of  actively 
decomposing  organic  matter,  such  as  that  in  sewage,  a 
complete  reduction,  even  to  the  liberation  of  nitrogen, 
may  occur. 

Deep  Water.— Water  which  penetrates  the  fissures  of 
the  fundamental  rock-formations  may  pass  to  great  depths, 
and  by  following  the  lines  of  the  lowest  and  least  permeable 
strata  may  be  transported  to  points  far  removed  from  those 
at  which  it  was  originally  collected.  The  chemical  changes 
thus  induced  include  most  of  those  which  take  place  at 


20  HISTORY  AND   CLASSIFICATION. 

higher  points,  but  the  increase  of  pressure  and  temperature 
confers  increased  solvent  power.  Carbonic  acid  will 
accumulate  under  conditions  favorable  to  the  solution  of 
calcium,  magnesium,  and  iron  carbonates,  and  iron,  and 
manganese  oxids  may  be  converted  into  carbonates  and 
then  dissolved.  Sulfates  are  reduced  to  sulfids,  and  these 
subsequently,  by  the  action  of  carbonic  acid,  yield  hy- 
drogen sulfid.  Organic  matter,  living  and  dead,  plays 
an  important  part,  determining  the  reduction  of  ferric 
compounds  to  ferrous,  and  of  the  sulfates  to  sulfids,  and 
is  itself  converted  ultimately  into  ammonium  compounds, 
notable  quantities  of  which  are  often  found  in  deep  waters. 
Further,  it  is  found  that  nitrates  and  nitrites  are  present 
only  in  small  amount,  except  from  certain  strata  rich  in 
organic  matter.  In  some  cases  the  water  acquires  very 
high  temperature,  and  dissociation  of  rocks  occurs  writh 
solution  of  considerable  amounts  of  silicic  acid,  which  is 
ordinarily  but  sparingly  soluble  in  water. 

Masses  of  wrater  thus  accumulated  under  heat  and  pres- 
sure may  find  their  way  to  the  surface  either  through 
natural  fissures  or  be  reached  by  borings. 

While  no  absolute  unchangeable  line  can  be  drawn  be- 
tween deep  and  subsoil  waters,  yet  it  will  in  most  cases  be 
found  that  the  deep  water  of  a  given  district,  whether 
obtained  through  natural  or  artificial  channels,  will  be 
decidedly  different  in  composition  from  the  subsoil  or  sur- 
face water  of  the  same,  and  that  the  rocks  passed  through 
in  such  cases  will  be  characterized  by  one  or  more  strata, 
difficultly  permeable  to  water,  and  therefore  preventing 
direct  communication.  The  characteristic  differences  be- 


DEEP   WATER.  21 

tween   surface,   subsoil,   and   deep   waters   are   clearly   in- 
dicated in  the  table  of  analyses  given  in  the  appendix. 

The  fact  that  mere  depth  is  not  the  essential  difference 
between  the  two  classes  of  waters  is  shown  by  comparison 
between  the  composition  of  the  water  from  a  well  at  Barren 
Hill,  near  the  northern  border  of  Philadelphia  County, 
and  a  deep  well  at  Locust  Point,  Baltimore.  The  former 
is  a  dug  well,  130  feet  deep;  the  latter  is  an  artesian  boring 
of  128  feet,  which  in  its  descent  passes  through  4  feet  of 
solid  rock.  The  deeper  well  is  evidently  supplied  by 
subsoil  water.  The  artesian  well,  though  located  100 
yards  from  a  brackish,  sewage-laden  estuary,  evidently 
derives  no  water  from  it. 

BARREN  HILL  LOCUST  POINT 

WELL.  WELL. 

Total  solids, 470.00       Less  than  100.00 

Chlorin, /___i2O.oo  4.68 

Nitrogen  as  nitrates, 22.00  none 


ANALYTIC    OPERATIONS. 


SANITARY  EXAMINATIONS. 

COLLECTION  AND  PRELIMINARY  EXAMINATION 
OF  SAMPLES. 

Great  care  must  be  taken  in  collecting  water  samples, 
in  order  to  secure  a  fair  representation  of  the  supply  and 

to  avoid  introduction  of 
foreign  matters.  The 
five-pint  green  glass- 
stoppered  bottles  used 
for  holding  acids  are 
suitable  for  containing 
the  samples.  The  con- 
tents of  one  such  bottle 
will  suffice  for  most 
sanitary  or  technic  ex- 
aminations. Figure  i 
shows  a  boxed  bottle 
known  as  "  Banker's 
Glass  Can,"  which  I 
FIG.  i.  have  found  very  con- 

venient for  transporta- 
tion. It  is  provided  with  a  hinged  lid  which  can  be 
fastened,  if  deemed  necessary,  by  a  padlock.  The  green 
glass-stoppered  bottles  may  be  fitted  in  such  an  arrange- 

22 


SANITARY   EXAMINATIONS.  23 

ment.  Crated  demijohns  are  now  made  for  forwarding 
water.  The  larger  sizes  are  well  adapted  for  samples 
which  are  to  be  subjected  to  elaborate  analysis.  A  boxed 
bottle  called  the  "New  Era  demijohn"  is  suitable  for  water 
samples.  Stone  jugs,  casks,  or  metal  vessels  should  not 
be  employed.  The  bottles  used  must  be  thoroughly  rinsed 
several  times  with  the  water  to  be  examined,  filled,  and  the 
stopper,  tied  down  or  fastened  by  stretching  a  rubber 
finger-cot  over  the  stopper  and  lip.  If  corks  are  used, 
they  should  be  new  and  thoroughly  rinsed.  Wax,  putty, 
plaster,  or  similar  material  should  not  be  used. 

In  taking  samples  from  lakes,  slow  streams,  or  reser- 
voirs, it  is  necessary  to  submerge  the  bottle  so  as  to  avoid 
collecting  any  water  that  has  been  in  immediate  contact 
with  the  air.  In  the  examination  of  public  water-supplies, 
the  sample  should  be  drawn  from  a  hydrant  in  direct  con- 
nection with  the  main,  and  not  from  a  cistern,  storage-tank, 
or  dead  end  of  a  pipe.  In  the  case  of  pump-wells,  a  few 
gallons  of  water  should  be  pumped  out  before  taking  the 
sample,  in  order  to  remove  that  which  has  been  standing 
in  the  pipe. 

In  all  cases  care  should  be  taken  to  fill  the  vessel  with 
as  little  agitation  with  air  as  possible. 

It  is  important  that  with  each  sample  a  record  be  made 
of  those  surroundings  and  conditions  which  might  in- 
fluence the  character  of  the  water,  particularly  in  reference 
to  sources  of  pollution,  such  as  proximity  to  cesspools, 
sewers,  or  manufacturing  establishments.  The  character 
and  condition  of  the  different  strata  of  the  locality  should 
be  noted  if  possible. 

Determinations  of  nitrogen  existing  as  ammonium  com- 


ANALYTIC   OPERATIONS. 


pounds  and  as  organic  matter,  and  of  oxygen-consuming 
power,  should  be  made  upon  the  sample  in  the  original 
condition,  whether  turbid  or  clear,  but  all  other  estima- 
tions should  be  made  upon  the  clear  liquid. 
Turbid  waters  may  be  clarified  by  stand- 
ing or  by  filtration;  for  the  latter  purpose 
Schleicher  &  Schull's  extra  heavy  No.  598 
paper  is  the  best.  In  many  cases  the  sus- 
pended matter  can  not  be  entirely  removed 
by  filtration,  and  subsidence  must  be  re- 
sorted to.  The  use  of  a  small  quantity  of 
alum,  or  aluminum  hydroxid,  as  described 
in  the  section  on  the  purification  of  water, 
will  sometimes  be  applicable  as  a  means  of 
clarifying  samples.  For  the  quantitative 
determination,  the  sediment  from  a  known 
volume  of  the  water  is  collected  on  a  tared 
filter,  dried,  and  weighed. 

The  water  from  newly-dug  wells  is 
generally  turbid,  and  the  determinations 
are  best  made  after  filtration;  but  the 
results  will  be  unsatisfactory,  showing  a 
higher  proportion  of  organic  matter  than 
will  be  found  when  the  supply  becomes 
clear.  For  taking  samples  at  consider- 
able depths  the  bottle  shown  in  Fig.  2 
will  answer,  but  samples  so  collected  will 
not  serve  for  determination  of  dissolved 


FIG.  2. 


gases. 


Collection    of    Samples    for    Bacteriologic    Exam- 
ination.— Bacteriologic   examinations   are   of  little   value 


SANITARY   EXAMINATIONS.  25 

unless  made  promptly  on  samples  that  have  been  collected 
with  precautions  against  contamination.  The  inoculation 
of  the  culture-medium  is  best  done  at  the  source.  If  this 
is  not  possible,  glass-stoppered  bottles  holding  about 
200  c.c.,  which  have  been  thoroughly  sterilized,  with 
stoppers  in  place,  in  a  hot-air  oven  at  100°  C.,  must  be 
used  for  collection.  They  should  be  rinsed  on  the  outside 
with  the  water,  dipped  below  the  surface,  the  stopper 
withdrawn,  and  again  inserted  when  the  bottle  is  full.  If 
these  are  to  be  transported  any  distance,  they  should  be 
packed  in  ice.  For  the  collection  of  samples  below  the 
surface  of  the  water,  the  bottle  shown  in  the  cut  (Fig.  2) 
is  recommended  by  Abbott.  The  bottle  having  been  pre- 
viously thoroughly  sterilized  is  sunk  to  the  proper  depth  and 
the  stopper  is  then  lifted  by  a  special  cord  and  held  until  the 
bottle  is  full,  when,  the  cprd  being  released,  the  stopper 
falls.  Before  taking  out  portions  for  test  the  lip  and  stopper 
must  be  thoroughly  sterilized  by  strong  alcohol  and  by  care- 
ful heating,  and,  after  cooling,  washing  with  sterilized 
water. 

Color. — A  colorless  glass  tube,  two  feet  long  and  two 
inches  in  diameter,  is  closed  at  each  end  with  a  disc  of 
colorless  glass.  An  opening  for  filling  and  emptying  the 
tube  should  be  made  at  one  end,  either  by  cutting  a  small 
segment  off  the  glass  disc,  or  cutting  out  a  small  segmental 
section  of  the  tube  itself  before  the  disc  is  cemented  on. 
A  good  cement  for  such  purposes  is  the  following: 

Caoutchouc, 2  parts. 

Mastic, 6 

Chloroform, 100      " 


26  ANALYTIC   OPERATIONS. 

The  ingredients  are  mixed  and  allowed  to  stand  for  a 
few  days.  The  cement  should  be  used  as  soon  as  solution 
is  effected,  as  it  becomes  viscid  on  standing. 

The  tube  must  be  about  half  filled  with  the  water  to  be 
examined,  brought  into  a  horizontal  position,  level  with 
the  eye,  and  directed  toward  a  brightly  illuminated  white 
surface.  The  comparison  of  tint  has  to  be  made  between 
the  lower  half  of  the  tube  containing  the  water  under  ex- 
amination and  the  upper  half  containing  air  only. 

A  more  convenient  form  of  tube  is  made  by  attaching 
brass  screw-nipples  to  each  end  of  the  tube,  and  closing 
these  by  screw-caps  carrying  plate-glass  discs.  Such  tubes 
can  be  obtained  from  dealers  in  chemical  apparatus.  It  is 
obvious  that  various  methods  of  comparing  color  and  tur- 
bidity may  be  devised,  but  data  so  obtained  are  of  little 
analytic  value,  and  even  that  little  is  limited  to  samples 
closely  analogous  in  character. 

Hazen  has  devised  a  standard  for  color  comparison 
which  he  claims  as  capable  of  most  satisfactory  use  on 
all  ordinary  waters.  It  is  based  upon  the  modification  of 
a  solution  of  platinum  chlorid  by  a  solution  of  cobalt 
chlorid,  as  follows: 

1.246  grams  of  potassium  platinum  chlorid  (correspond- 
ing to  0.5  gram  of  Pt)  and  i  gram  of  cobalt  chlorid  (corre- 
sponding to  0.25  gram  of  Co)  are  dissolved  in  water,  100 
c.c.  of  strong  hydrochloric  acid  added,  and  the  solution 
made  up  to  1000  c.c.  It  keeps  well,  even  when  exposed 
to  the  light.  For  comparison,  i,  2,  3,  etc.,  of  the  stock 
solution  are  diluted  to  50  c.c.  in  Nessler  tubes.  These 
correspond  to  o.i,  0.2,  0.3,  etc.,  degrees  of  the  color  standard. 
These  also  keep  for  a  long  time  if  protected  from  dust. 


SANITARY   EXAMINATIONS.  27 

Direct  comparison  in  200  mm.  tubes  is  generally  sufficient. 
If  the  shade  of  color  is  not  exactly  that  of  the  water,  more 
cobalt  may  be  added,  the  platinum  being  constant.  Hazen 
expresses  the  result  in  any  case  in  terms  of  "the  amount 
of  platinum  in  parts  per  10,000,  which  in  acid  solution 
with  so  much  cobalt  as  will  match  the  hue,  produces  an 
equal  color  in  distilled  water." 

Lovibond's  tintometer  is  probably  the  best  means  of 
making  color  comparisons. 

Odor. — Put  about  150  c.c.  of  the  water  into  a  clean, 
wide-mouth  250  c.c.  stoppered  bottle,  which  has  been 
previously  rinsed  with  the  same  water;  insert  the  stopper 
and  warm  the  water  in  a  water-bath  to  100°  F.  Remove 
the  bottle  from  the  water-bath  and  shake  it  rapidly  for  a 
few  seconds;  remove  the  stopper,  and  immediately  note  if 
the  water  has  any  smellv  Insert  the  stopper  and  repeat 
the  test. 

In  a  polluted  water  the  odor  will  sometimes  give  a  clue 
to  the  origin  of  the  pollution. 

Turbidity. — Several  methods  for  expressing  degree  of 
turbidity  have  been  used.  Whipple  and  Jackson,  after 
comparing  these,  find  that  finely  powdered  diatomaceous 
earth  is  satisfactory.  The  material  is  ignited,  ground  to  a 
powder  that  will  pass  through  a  2oo-mesh  sieve,  dried  at 
1 00°  C.,  cooled  in  a  desiccator,  and  kept  in  a  well-stoppered 
bottle.  A  strong  standard  is  prepared  by  adding  i  gram 
of  this  powder  to  i  liter  of  water,  and  12  dilute  standards 
by  mixing  quantities  of  the  strong  standard  in  amount 
from  i  to  10  c.c.,  increasing  by  0.5  c.c.,  to  quantities  of 
distilled  water  sufficient  to  make  100  c.c.  in  each  case. 
The  dilute  standards  are  kept  in  tightly  corked  tubes  and 


28  ANALYTIC   EXAMINATIONS. 

shaken  several  times  when  used  for  comparison.  If  new 
corks  are  used,  they  should  well  boiled  in  water  to  extract 
coloring-matter.  If  the  sample  is  of  high  turbidity,  it 
must  be  diluted  by  a  known  volume  of  water.  The  record 
is  made  by  noting  the  strength  of  the  standard  tube  that 
is  nearest  in  turbidity  to  the  sample,  the  tubes  being  held 
together  and  viewed  from  the  side.  The  tube  containing 
the  sample  must  be  uniform  in  size  and  quality  with  those 
containing  the  standard. 

Reaction. — The  determination  of  reaction  is  usually 
made  by  the  addition  of  a  neutral  solution  of  litmus  to  the 
water.  If  an  acid  reaction  is  obtained,  the  water  should 
be  boiled  in  order  to  determine  if  it  is  due  to  carbonic 
acid.  Some  of  the  more  delicate  indicators,  such  as 
phenolphthalein,  lakmoid,  and  erythrosin,  may  be  used 
with  advantage  for  these  tests.  The  latter  possesses  the 
advantage  that  it  is  unaffected  by  carbonic  acid,  but  de- 
tects even  traces  of  free  mineral  acid.  It  is  neutral,  also, 
to  many  normal  metallic  salts,  such  as  ferrous  sulfate, 
which  are  acid  to  litmus.  Ferric  salts,  however,-  are  acid 
to  lakmoid.  Its  color-changes  are  the  same  as  those  of 
litmus — /.  e.,  red  with  acids  and  blue  with  alkalies. 

Phenolphthalein  is  usually  applied  to  the  detection  of 
weak  acids,  such  as  carbonic  acid  and  the  organic  acids. 
In  acid  and  neutral  solutions  it  is  colorless;  in  alkaline, 
red.  Nearly  all  waters  contain  carbonic  acid,  and  will 
therefore  bleach  a  solution  of  phenolphthalein  which  has 
been  reddened  by  a  small  amount  of  alkali. 


SANITARY   EXAMINATIONS. 


29 


TOTAL  SOLIDS. 

A  platinum  basin  holding  100  c.c.  will  be  found  con- 
venient for  this  determination.  This  will  weigh  about 
45  grams.  It  should  be  kept  clean  and  smooth  by  fre- 
quent burnishing  with  sand,  a  little  of  which  should  be 
placed  in  the  palm  of  the  hand,  moistened,  and  the  dish 
gently  rubbed  against  it.  Very  fine  sea-sand  with  round, 
smooth  grains  is  the  only  kind  suitable  for  this  purpose. 
Coarse  river  sand,  tripoli,  or  other  rough  scouring-powders 
must  not  be  employed.  If  proper 
care  is  taken,  the  luster  of  the 
metal  will  be  retained,  and  the 
loss  in  weight  will  be  trifling. 
The  inner  surface  can  generally 
be  cleaned  by  treatment,  with 
hydrochloric  acid,  rinsing,  and, 
if  necessary,  burnishing  with 
sand.  Neglect  of  these  precau- 
tions will  soon  lead  to  serious 
damage  to  the  dish.  A  small, 
smooth  slab  of  iron  or  marble  is 

convenient  to  set  it  on  while  cooling.  When  being  heated 
over  the  naked  flame,  the  dish  should  rest  on  a  triangle  of 
iron  wire,  covered  with  pipe-stems.  Dishes  of  pure  nickel 
are  not  satisfactory  substitutes  for  those  of  platinum. 

Platinum-pointed  forceps  should  be  used  in  handling 
the  dish.  The  platinum  terminals  may  be  kept  bright 
and  clean  by  the  use  of  sand. 

The  low-temperature  burner,  used  as  shown  in  figure  3, 
will  be  found  a  very  convenient  substitute  for  the  water- 


FIG.  3. 


30  ANALYTIC   OPERATIONS. 

bath  and  hot-air  oven.  The  inlet  pipe  is  very  short  and 
soon  becomes  so  hot  as  to  injure  the  rubber  tube.  To 
avoid  this  it  may  be  lengthened  by  means  of  a  piece  of 
J-inch  gas-pipe,  or  the  junction  may  be  wrapped  with  a 
rag,  the  ends  of  which  dip  into  water.  By  capillary  at- 
traction the  rag  is  kept  moist  and  cool. 

The  determination  of  total  solids  is  made  by  evaporating 
100  c.c.  of  the  water  in  the  platinum  basin,  which  has 
been  previously  heated  almost  to  redness,  allowed  to  cool 
for  ten  minutes,  and  weighed.  The  operation  is  conducted 
at  a  moderate  heat.  When  the  residue  appears  dry,  the 
heat  may  be  increased  slightly  for  some  minutes.  The 
above  method  will  answer  in  most  cases.  In  waters  of 
exceptional  purity  it  may  be  advisable  to  use  larger  quan- 
tities, such  as  250  c.c.  When  the  residue  contains  deli- 
quescent bodies,  the  determination  will  not  be  accurate, 
and  when  appreciable  amounts  of  magnesium  and  chlorin 
are  present,  a  decomposition  will  occur  toward  the  close 
of  the  evaporation  by  which  magnesium  oxid  will  be  formed 
and  hydrogen  chlorid  escape. 

The  irregular  decomposition  occurring  during  the  evap- 
oration may  be  largely  prevented  by  adding  0.005  gram  of 
sodium  carbonate  to  each  100  c.c.  of  the  sample  taken. 
This  converts  magnesium  and  calcium  salts  into  carbonates. 
The  sodium  carbonate  is  conveniently  kept  in  the  form  of 
solution  of  such  strength  that  i  c.c.  contains  o.ooi  gram. 
The  weight  of  the  carbonate  is,  of  course,  to  be  deducted 
from  the  weight  of  the  residue.  Drown  and  Hazen  have 
carefully  investigated  this  method  and  have  found  it  avail- 
able for  a  more  satisfactory  determination  of  the  loss  on 
ignition.  For  this  process  they  place  the  platinum  basin 


SANITARY   EXAMINATIONS.  31 

containing  the  residue  within  another  similar  basin  of  such 
size  that  an  air-space  of  about  one-half  of  an  inch  is  left  all 
around  the  inner  dish,  which  is  supported  upon  a  spiral  of 
platinum  that  rests  on  the  bottom  of  the  outer' dish.  Over 
the  inner  dish  is  suspended  a  disc  of  platinum  foil  to  reflect 
the  heat.  The  outer  dish  is  heated  to  bright  redness. 

After  the  weight  of  the  residue  is  obtained,  the  dish 
should  be  cautiously  heated  to  low  redness  and  the  effect 
noted.  Nitrates  and  nitrites,  calcium  and  magnesium 
carbonates,  are  decomposed;  ammonium  salts  are  driven 
off;  potassium  and  sodium  chlorids  are  also  driven  off 
if  the  temperature  is  high.  Organic  matter  is  at  first 
charred,  and  by  continued  heating  burned  off.  When  the 
quantity  of  nitrates  is  considerable,  slight  deflagration  may 
be  observed,  or  the  production  of  red  fumes  of  nitrogen 
dioxid.  The  organic  matter,  in  decomposing,  not  infre- 
quently develops  odors  which  indicate  its  character  or 
source.  These  are  more  satisfactorily  observed  when  a 
rather  large  quantity,  say  250  c.c.,  is  evaporated  at  a  low 
heat,  preferably  on  a  water-bath. 

In  water  of  high  organic  purity,  the  residue  on  heating 
will  give  no  appreciable  blackening  nor  odor,  while  in 
forest  streams  charged  with  vegetable  matter  derived  from 
falling  leaves,  very  decided  blackening  without  unpleasant 
odor  will  be  noticed.  The  loss  of  weight  after  heating 
can  not  be  taken  as  a  measure  of  the  organic  matter,  ex- 
cept when  present  in  relatively  large  amount. 


32  ANALYTIC   OPERATIONS. 

CHLORIN. 

Solutions  Required: 

Standard  Silver  Nitrate. — Dissolve  about  five  grams  of 
pure  re  crystallized  silver  nitrate  in  distilled  water,  and 
make  the  solution  up  to  1000  c.c.  The  amount  of  chlorin 
to  which  this  is  equivalent  may  be  determined  as  follows: 
Several  grams  of  pure  sodium  chlorid  are  finely  powdered 
and  heated  over  a  Bunsen  burner  for  five  minutes,  not  quite 
to  redness.  When  cold,  0.824  gram  are  dissolved  in  water 
and  the  solution  made  up  to  500  c.c.  Twenty-five  c.c.  of 
this  should  be  treated  as  below,  and  the  amount  of  silver 
solution  required  noted.  Each  c.c.  of  the  sodium  chlorid 
solution  is  equivalent  to  o.ooi  gram  chlorin. 

Potassium   Chromate. — Five   grams   of  potassium   chro- 
mate  are  dissolved  in  100  c.c.  of  distilled  water.     A  solu- 
tion of  silver  nitrate  is  added  until  a  permanent  red  pre- 
cipitate is  produced,  which  is  separated  by  filtration. 
Analytic  Process : 

If  a  preliminary  test  shows  the  chlorin  to  be  present  in 
considerable  amount,  the  determination  may  be  made  on 
100  c.c.  of  the  water  without  concentration.  If,  how- 
ever, there  is  but  little  present,  250  c.c.  should  be  evap- 
orated to  about  one-fifth,  best  with  the  addition  of  a  little 
sodium  carbonate,  and  the  determination  made  on  the 
concentrated  liquid  after  cooling. 

The  water  is  placed  in  a  porcelain  dish  or  in  a  beaker 
standing  on  a  white  surface,  a  few  drops  of  potassium 
chromate  solution  added,  and  standard  silver  nitrate  solu- 
tion run  in  from  a  buret  until  a  faint  red  color  of  silver 
chromate  remains  permanent  on  stirring.  The  proportion 


SANITARY   EXAMINATIONS.  33 

of  chlorin  is  then  calculated  from  the  number  of  c.c.  of 
silver  solution  added.  Greater  accuracy  is  secured  by 
operating  in  yellow  light.  A  second  determination  may 
be  made,  using  as  a  comparison  the  liquid  first  titrated, 
the  red  color  having  been  previously  discharged  by  a  few 
drops  of  sodium  chlorid  solution. 

The  water  should  always  be  as  nearly  neutral  as  possible 
before  titration.  If  acid,  it  may  be  neutralized  by  the 
addition  of  sodium  carbonate. 

The  residue  obtained  by  evaporating  the  water  with 
sodium  carbonate,  as  described  in  connection  with  the  de- 
termination of  the  total  solids,  will  often  serve  conveni- 
ently for  estimating  the  chlorin.  It  is  best  to  use  200  c.c. 
of  the  sample  and  redissolve  the  residue  in  about  50  c.c. 
of  distilled  water,  rubbing  the  sides  of  the  dish  well  with  a 
rubber-tipped  rod,  and  the,n  titrating  as  indicated  above. 

Chlorin  may  be  determined  by  Volhard's  method, 
adding  excess  of  standard  silver  solution,  and  then  titrating 
the  residual  silver  by  means  of  thiocyanate  solution.  Free 
nitric  acid  does  not  interfere  with  this  method,  but  it  is 
necessary  to  remove  the  silver  chlorid  before  titrating  with 
thiocyanate.  The  following  description  of  the  method 
is  adapted  from  Button's  "Volumetric  Analysis": 
Solutions  Required : 

Decinormal  Thiocyanate. — About  10  grams  of  the 
potassium  compound  or  8  grams  of  the  ammonium  com- 
pound are  dissolved  in  a  liter  of  water  and  the  solution 
adjusted  by  means  of  standard  silver  nitrate  solution. 

Decinormal  Silver  Nitrate. — This  may  be  prepared  by 
dissolving  pure  silver  in  nitric  acid,  since  as  noted  above  a 
slight  excess  of  the  acid  does  not  interfere  with  the  test, 
c 


34  ANALYTIC   OPERATIONS. 

Ferric  Indicator, — A  saturated  solution  of  ammonium 
ferric  sulfate. 

Nitric  A  cid. — This  must  be  free  from  the  lower  oxids 
of  nitrogen.     They  may  be  removed  by  adding  about  one- 
fourth  volume  of  water  and  boiling   until  colorless.      The 
acid  should  be  kept  from  the  light. 
Analytic  Method : 

f  A  suitable  quantity  of  the  water  is  treated  with  a  slight 
excess  of  decinormal  silver  nitrate,  the  chlorid  collected  by 
shaking,  and  an  aliquot  part  of  the  liquid  removed  by 
decantation  or  nitration.  To  this  is  added  10  c.c.  of  the 
nitric  acid  and  5  c.c.  of  the  ferric  indicator,  and  thiocyanate 
is  run  in  until  a  faint  permanent  brown  is  produced  in  the 
liquid.  This  marks  the  precipitation  of  all  the  silver,  and 
the  formation  of  ferric  thiocyanate.  The  color  is  seen  best 
by  holding  the  flask  against  a  background  of  white  paper. 
As  the  point  of  precipitation  of  the  last  portions  of  silver 
is  approached,  the  precipitate  becomes  flocculent  and 
settles  easily.  The  excess  of  silver  is  deducted  from  the 
total  used;  the  remainder  is  the  amount  required  for  the 
chlorin  in  the  water. 

NITROGEN  IN  AMMONIUM  COMPOUNDS  AND  IN 
ORGANIC  MATTER. 

Apparatus  Required : 

Distilling  Apparatus. — That  shown  in  figure  4  has  been 
found  to  be  convenient.  The  still  consists  of  a  glass 
retort  of  about  1000  c.c.  capacity.  The  beak  of  the  retort 
should  incline  slightly  upward,  to  prevent  contamination 
by  splashing.  At  about  seven  centimeters  from  the  end 
it  should  be  bent  at  a  right  angle,  and  drawn  out  so  as  to 


SANITARY   EXAMINATIONS. 


35 


enter  the  condensing  worm  for  such  a  distance  as  to  ter- 
minate beneath  the  level  of  the  water. 

The  condenser  shown  in  the  figure  is  a  copper  tank, 
33  cm.  high,  15  cm.  wide,  and  of  length  proportioned  to 
the  number  of  distilling  vessels  operated.  The  condensing 
tube  is  shown  only  as  emerging  from  the  bottom  of  the  tank. 


FIG.  4. 

Glass  worms  are  apt  to  break,  and  it  is  more  satisfac- 
tory to  use  block  tin.  A  piece  of  rubber  tubing  is  drawn 
over  the  junction  between  the  retort  neck  and  worm.  A 
rapid  current  of  cold  water  should  be  maintained  through 
the  condenser.  The  heat  is  applied  by  means  of  the  low- 


36  ANALYTIC   OPERATIONS. 

temperature  burner,  the  iron  ring  of  which  is  removed  so 
that  the  retort  rests  directly  on  the  gauze. 

To  prevent  overheating  of  the  upper  part  of  the  retort, 
a  sheet  of  thick  asbestos  board  about  20  cm.  in  diameter, 
with  a  central  opening  about  5  cm.  in  diameter,  may  be 
placed  on  the  gauze.  With  this  arrangement  the  heat  is 
under  control,  and  the  danger  of  breaking  the  retort  is 
slight.  It  is  advisable  to  protect  the  retort  from  drafts 
of  cold  air,  which  may  be  done  with  a  cone  made  of  thin 
sheet  asbestos. 

Figure  5  shows  the  distilling  arrangement  used  in  the 
laboratory  of  the  testing  station  of  the  Philadelphia  ni- 
tration plant.  The  cut  was  loaned  by  the  Journal  0}  the 
American  Chemical  Society,  and  the  description  is  tran- 
scribed from  the  paper  published  in  that  journal  by  G.  E. 
Thomas  and  C.  A.  Hall.  The  flask  has  a  side-neck  and 
ground-glass  stopper,  and  bulb  of  a  capacity  of  nearly 
2000  c.c.  It  is  supported  on  wire  gauze  resting  on  a  sheet- 
iron  cylinder.  The  condensing  worm  is  of  block  tin  con- 
nected to  the  side-neck  by  rubber  tubing,  the  glass  extending 
into  the  tin  for  several  centimeters  beyond  the  point  of 
contact  of  the  rubber.  Another  piece  of  rubber  tubing 
covers  the  point  of  contact  of  the  first  piece  with  the  metal 
tube.  The  latter  is  about  9  mm.  internal  diameter,  about 
12  mm.  external,  and  is  coiled  into  a  helix  6  cm.  internal 
diameter  and  n  cm.  pitch.  The  caliber  of  the  tube  is 
expanded  slightly  at  the  upper  end  to  allow  of  insertion 
of  the  side-neck  of  the  flask  and  is  contracted  for  a  few 
centimeters  at  the  outlet.  The  condenser  is  made  of  cold 
rolled  sheet-copper  (commercially  known  as  24  ounce), 
braced  within  and  provided  with  a  lid  hinged  at  the  back 


SANITARY   EXAMINATIONS. 


37 


and  overlapping  slightly  in  front.  The  water  is  supplied 
below  and  overflows  at  the  top.  The  ground  stoppers  and 
side-neck  attachment  permit  of  introduction  of  samples 
and  solutions  without  disconnecting  the  flasks.  A  long- 
necked  funnel  will  be  convenient  for  this  purpose. 


Figure  6  shows  an  elaborate  distilling  apparatus  ar- 
ranged by  R.  S.  Weston.  It  has  the  advantage  that  the 
distillate  is  received  on  the  side  on  which  the  distilling 


ANALYTIC   OPERATIONS. 


C/arrrjo 


FIG.  6. 


SANITARY   EXAMINATIONS. 


39 


flask  is  placed.  The  details  of  construction  are  indicated 
in  the  figure.  The  condenser  may  be  made  of  copper  or 
japanned,  galvanized  iron. 


Scale  lMin.=  l  foot. 

FIG.  7. 


Another  convenient  form  of  apparatus  is  shown  in  figure 
7.     It  is  employed  in  the  laboratory  of  the  Massachusetts 


ANALYTIC   OPERATIONS. 


State  Board  of  Health.  The  joint  between  the  flask  and 
condenser  is  made  by  means  of  a  sound  cork,  into  which 
the  condensing  tube  fits  closely;  the  tube  from  the  flask 
is  made  slightly  smaller  than  the  condensing  tube,  and 
passes  into  it  for  about  four  centimeters. 

A  form  of  condenser  applicable  to  distillations  of  this 
character  has  been  devised  by  Cribb 
and  is  shown  in  figure  8.  The  vapor 
passes  to  a  narrow  annulus  by  the 
tube  A;  the  cooling  water  enters 
the  central  portion  and  overflows, 
running  down  the  outside  wall, 
being  collected  by  the  projecting 
rim  and  carried  off  by  the  tube  G. 
For  water  analysis  a  retort  with  the 
neck  bent  at  an  obtuse  angle  may 
be  used,  or  a  flask  with  side  tube. 
\  i  JJJY  In  the  latter  case,  the  tube  must 

\J^T~[    )  leave   the   flask   at   a  slight  angle 

upward,  and  about  midway  be  bent 
at  a  slight  obtuse  angle  downward. 
This  prevents  contamination  of  the 
distillate  by  spurting.  The  draw- 
ing shows  the  form  given  by  Cribb, 
but  experience  has  shown  that 

more  space  should  be  allowed  between  the  inner  and 
outer  wall  at  the  lowest  point,  and  that  the  catch-basin 
should  be  large.  The  tube,  G,  should  be  at  least  three 
times  the  caliber  of  F.  It  will  often  be  advantageous  to 
wrap  a  piece  of  muslin  around  the  body  of  the  apparatus. 
Cylinders  /or  Comparison-color  Tests,  about  2.5  centi- 


FIG.  8. 


SANITARY   EXAMINATIONS.  41 

meters  in  diameter  and  holding  100  c.c.,  made  of  colorless 

glass. 

Solutions  Required : 

Sodium  Carbonate. — Fifty  grams  of  pure  sodium  carbon- 
ate are  strongly  heated,  dissolved  in  250  c.c.  of  distilled 
water,  and  the  solution  boiled  down  to  200  c.c. 

Ammonium-jree  Water. — If  the  distilled  water  of  the 
laboratory  gives  a  reaction  with  Nessler  reagent,  it  should 
be  treated  with  sodium  carbonate,  about  one  grain  to  the 
liter,  and  boiled  until  about  one-fourth  has  been  evapo- 
rated. Ammonium-free  water  may  be  obtained  by  distill- 
ing, in  a  retort,  water  made  slightly  acid  with  sulfuric  acid. 

Messrs.  J.  B.  Weems,  C.  E.  Gray,  and  E.  C.  Myers  re- 
commend the  following  method:  Sodium  dioxid  is  added 
to  ordinary  water  in  the  proportion  of  one  gram  to  a  liter, 
and  the  liquid  boiled  for  thirty  minutes,  or  longer  if  the 
amount  of  ammonium  compounds  is  high.  It  is  then 
cooled  and  the  flask  kept  closed.  Flasks  holding  several 
liters  are  most  convenient.  If  the  water  be  distilled,  the 
distillate  may  also  be  used  for  the  preparation  of  standard 
nitrate  and  nitrite  solutions. 

Standard  Ammonium  Chlorid. — Dissolve  0.382  gram  of 
pure  dry  ammonium  chlorid  in  100  c.c.  of  ammonium- 
free  water.  For  use,  dilute  i  c.c.  of  this  solution  with 
pure  water  to  100  c.c.  One  c.c.  of  this  dilute  solution  con- 
tains o.ooooi  gram  of  nitrogen. 

Nessler  Reagent. — Dissolve  35  grams  of  potassium  iodid 
in  100  c.c.  of  water.  Dissolve  17  parts  of  mercuric  chlorid 
in  300  c.c.  of  water.  The  liquids  may  be  heated  to  aid 
solution,  but  must  be  cooled  before  use.  Add  the  mercuric 
chlorid  solution  to  that  of  the  potassium  iodid,  until  a 


42  ANALYTIC   OPERATIONS. 

permanent  precipitate  is  produced.  Then  dilute  with  a 
20  per  cent,  solution  of  sodium  hydroxid  to  1000  c.c.,  add 
mercuric  chlorid  solution  until  a  permanent  precipitate 
again  forms,  and  allow  to  stand  until  clear.  Nessler  and 
other  reagents  are  best  kept  in  glass-capped  bottles,  figure 
9,  in  which  the  pipet  may  remain  when  not  in 
use.  The  solution  improves  by  keeping. 

Alkaline  Potassium  Permanganate.— Dissolve 
200  grams  of  potassium  hydroxid,  in  sticks,  and 
8  grams  of  potassium  permanganate,  in  a  liter 
of  distilled  water. 

The  solution  may  be  boiled  until  about  one- 
FIG.  9.  fourth  is  evaporated,  and  then  made  up  to  a 
liter  with  ammonium-free  water.  It  will  still 
furnish  some  ammonium.  Fox  recommends  to  distil  50 
c.c.  with  500  c.c.  of  absolutely  ammonium-free  water,  best 
twice  distilled  with  sulfuric  acid,  and  note  the  ammonia 
obtained.  This  quantity  should  be  deducted  in  each  anal- 
ysis. The  method  of  determining  nitrogen  by  permanga- 
nate, as  given  below,  avoids  the  necessity  for  this  pre- 
liminary valuation  of  the  solution. 
Analytic  Process : 

The  retort  and  condenser  are  thoroughly  rinsed  with 
ammonium-free  water,  500  c.c.  of  the  water  to  be  tested 
introduced,  about  five  c.c.  of  the  sodium  carbonate  solu- 
tion added  to  render  the  water  alkaline,  and  some  small 
pieces  of  pumice-stone  or  fragments  of  pipe-stems  heated 
to  redness  and  dropped  in  wrhile  hot.  The  water  is  then 
boiled  gently  until  the  distillate  measures  50  c.c.  The 
distillate  is  transferred  to  one  of  the  color- comparison 
cylinders,  and  two  c.c.  of  Nessler  reagent  added.  A 


SANITARY   EXAMINATIONS.  43 

yellowish-brown  color  is  produced,  the  intensity  of  which 
is  proportional  to  the  amount  of  ammonium  present.  The 
full  color  is  developed  in  five  minutes.  This  color  is  ex- 
actly matched  by  introducing  into  another  cylinder  50 
c.c.  of  ammonium-free  water,  some  of  the  standard  am- 
monium chlorid  solution,-  and  two  c.c.  Nessler  reagent, 
as  before.  According  as  the  color  so  produced  is  deeper 
or  lighter  than  that  obtained  from  the  water,  other  com- 
parison liquids  are  prepared  containing  smaller  or  larger 
proportions  of  the  ammonium  chlorid,  until  the  proper 
color  is  produced. 

The  distillation  is  continued,  successive  portions  of  50 
c.c.  each  collected,  and  tested  until  no  reaction  occurs 
with  Nessler  reagent.  The  sum  of  the  figures  from  the 
several  distillates  gives  the  total  nitrogen  obtainable  as 
"free  ammonia,"  so  called. 

If  the  quantity  of  ammonium  is  sufficient  to  cause  a 
precipitate,  the  color  comparison  can  not  be  accurately 
made.  In  most  cases  this  will  not  be  of  serious  moment, 
as  the  quantity  will  be  beyond  the  allowable  limit.  If 
accurate  determination  be  desired,  it  may  be  made  by 
dividing  the  first  distillate  into  two  equal  parts,  nessleriz- 
ing  one  of  these,  and  then,  if  necessary,  diluting  the  second 
part  with  ammonium-free  water  and  nesslerizing  this. 

Occasionally,  the  evolution  of  ammonium  hydroxid 
continues  indefinitely,  and  may  even  increase  with  succes- 
sive distillates.  This  is  due,  not  to  ammonium  compounds 
existing  as  such,  but  to  decomposition  of  certain  nitro- 
genous bodies,  especially  urea.  In  this  case  it  is  not  ad- 
visable to  prolong  distillation  beyond  the  fourth  or  fifth 
distillate,  but  to  proceed  to  the  following  part  of  the  process. 


44  ANALYTIC   OPERATIONS. 

The  residue  in  the  retort  serves  for  the  determination 
of  the  nitrogen  which  is  convertible  into  ammonium  by 
alkaline  potassium  permanganate — the  so-called  "albu- 
minoid ammonia"  of  Messrs.  Wanklyn,  Chapman,  and 
Smith. 

Fifty  c.c.  of  alkaline  permanganate  solution  are  added 
to  the  retort,  the  distillation  resumed,  and  the  nitrogen 
estimated  in  each  50  c.c.  as  before,  deducting  that  yielded 
by  the  permanganate. 

It  is  a  practice  of  some  analysts  to  mix  the  distillates 
of  each  of  the  foregoing  operations,  and  make  determina- 
tions merely  of  the  total  nitrogen  in  each  case.  By  so 
doing,  valuable  information  may  be  lost,  since  it  has  been 
pointed  out  by  several  observers,  notably  Mallet  and 
Smart,  that  important  information  may  be  gained  by 
observing  the  rate  of  evolution  of  the  ammonium  hydroxid. 
Mallet  has  further  pointed  out  that  many  waters  may  con- 
tain substitution  ammoniums  which  may  pass  over  before 
the  addition  of  the  alkaline  permanganate,  but  not  be 
correctly  measured  by  nesslerizing.  To  avoid  this  error, 
he  suggested  that  two  determinations  be  made  on  each 
sample,  one  as  above  described,  and  the  other  by  the 
addition  of  alkaline  permanganate  without  previous  dis- 
tillation. A  higher  figure  may  be  obtained  than  the  total 
from  the  two  distillations  by  the  other  process. 

Since  small  quantities  of  ammonium  compounds  and 
nitrogenous  matters  are  everywhere  present,  the  greatest 
care  should  be  exercised  in  order  to  avoid  their  introduc- 
tion in  any  way  during  the  course  of  the  analysis.  All 
measuring  vessels,  cylinders,  etc.,  should  be  thoroughly 
rinsed  before  using.  The  temperatures  of  the  distillates 


SANITARY   EXAMINATIONS.  45 

and  standards  should  be  approximately  the  same  when  the 
colors  are  compared. 

The  Chemical  Section  of  the  American  Association  for 
the  Advancement  of  Science  recommended  the  following 
method  for  the  application  of  the  process: 

200  c.c.  of  distilled  water,  together  with  10  c.c.  of 
the  sodium  carbonate  solution,  are  distilled  down  to 
about  100  c.c.  in  the  retort  in  which  the  analysis  is  to 
be  conducted,  and  the  last  portion  of  50  c.c.  nesslerized 
to  assure  freedom  from  ammonium.  Then  500  c.c.  of  the 
water  to  be  examined  are  added,  and  the  distillation  is 
carried  on  at  such  a  rate  that  about  50  c.c.  are  collected 
in  each  succeeding  ten  minutes,  and  until  a  50  c.c.  measure 
of  distillate  is  obtained  containing  only  an  inappreciable 
quantity  of  ammonia.  In  nesslerizing,  five  minutes  are 
to  be  allowed  for  the  full  development  of  color;  after  this, 
no  change  takes  place  for  many  hours. 

The  distilling  vessel  is  emptied  and  rinsed  thoroughly, 
200  c.c.  of  distilled  water  and  50  c.c.  of  alkaline  perman- 
ganate solution  put  in,  and  the  liquid  distilled  down  to 
about  100  c.c.,  the  last  portions  of  the  distillate  being 
tested  to  ascertain  freedom  from  ammonium  compounds, 
another  portion  of  500  c.c.  of  the  water  to  be  tested  is  added, 
and  the  distillation  made  as  before.  The  difference  be- 
tween the  "free"  ammonia  of  the  first  operation  and  the 
total  ammonia  of  the  second  is  to  be  taken  as  the  "albu- 
minoid" ammonia. 

It  is  convenient  to  operate  the  distilling  flasks  in  pairs, 
using  one  of  each  pair  for  the  permanganate  process.  Delay 
and  trouble  of  rinsing  are  thus  avoided.  Before  beginning 
an  analysis,  the  greater  part  of  the  residue  from  a  previous 


46 


ANALYTIC   OPERATIONS. 


operation  may  be  drawn  off  with  a  siphon,  200  c.c.  of 
distilled  water  added  to  each,  and  the  liquids  distilled 
until  the  reagent  shows  freedom  from  ammonium  com- 
pounds. Suitable  portions  of  the  sample  are  then  put  in 
each  flask. 

For  nesslerizing  and  other 
color  comparisons,  many  forms 
of  apparatus  have  been  pro- 
posed. One,  devised  by  Hehner, 
is  shown  in  figure  10.  It  con- 
sists of  a  graduated  cylinder  with 
a  stop-cock  near  the  base,  by 
which  the  liquid  can  be  drawn 
down  at  will.  Two  such  cylin- 
ders may  be  used — one  for  the 
nesslerized  distillate,  the  other 
for  the  comparison  liquid.  The 

I 


8.5  cc 


FIG.  10. 


FIG.  ii  a. 


darker  liquid  is  drawn  out  until  the  tints  are  equal,  when 
the  relative  volumes  remaining  will  give  the  data  for  calcu- 
lation. 

H.  J.  Watson  has  modified  the  Hehner  tube  as  shown 
in  figure  n.      The  cuts  were  loaned  by  the  Amer.  Jour. 


SANITARY   EXAMINATIONS. 


47 


of  Pharmacy.  The  jar  is  30  cm.  long,  1.8  cm.  in  diameter, 
and  is  graduated  into  cubic  centimeters  for  about  20  cm. 
from  the  base.  At  the  side  of  the  base  a  small  tube  pro- 


Ul 


FIG.  ii  b. 


jects,  which  may  be  provided  with  a  stop-cock  but  it  will 
be  seen  from  one  of  the  figures  that  this  is  not  necessary. 


48  ANALYTIC   OPERATIONS. 

A  number  of  tubes  similar  in  size  and  quality  of  glass  to 
the  graduated  tube,  but  marked  only  at  50  c.c.,  should 
be  provided.  The  distillates  from  the  water  are  placed 
in  the  ungraduated  tubes,  and  compared  with  the  tints 
of  the  standard  ammonium  solution,  by  making  the 
volume  of  the  latter  in  the  graduated  tube  increase  or 
decrease  by  means  of  the  stop-cock  on  the  burette  and 
changing  the  height  of  the  latter. 

TOTAL  ORGANIC  NITROGEN. 

Several  processes  for  the  determination  of  the  organic 
nitrogen  in  water,  based  on  those  in  use  in  ordinary  organic 
analysis,  have  been  devised.  That  of  Frankland  and  Arm- 
strong requires  complex  and  extensive  apparatus  and 
special  skill,  has  been  shown  also  to  be  liable  to  inaccuracies, 
and  has  not  come  into  extended  use. 

The  ease  and  certainty  with  which  the  nitrogen  of  most 
organic  bodies  may  be  converted  into  ammonium  sulfate 
by  boiling  with  sulfuric  acid,  offers  a  means  of  determina- 
tion free  from  the  objections  of  former  methods.  The 
method  introduced  by  Kjeldahl  for  general  organic  analysis 
was  first  successfully  applied  to  water  analysis  by  Drown 
and  Martin. 

In  their  original  process,  500  c.c.  was  concentrated  to 
about  300  c.c.,  and  the  distillate  nesslerized  for  determin- 
ing the  nitrogen  existing  as  ammonium  compounds.  The 
organic  nitrogen  is  then  determined  in  the  residual  water. 
Owing  to  the  fact  that  organic  matter  may  be  decomposed 
by  moderate  heat,  there  is  liability  to  underestimation  of 
the  nitrogen.  It  is  best,  therefore,  to  determine  at  once 
the  total  unoxidized  nitrogen,  and  estimate,  without  dis- 


SANITARY   EXAMINATIONS.  49 

tillation,  on  a  separate  portion  of  the  sample,  the  nitrogen 
that    exists    in    ammonium    compounds.     The    procedure 
is  as  follows : 
Reagents  Required : 

Concentrated  Suljuric  Acid. — This  should  be  as  free  as 
possible  from  nitrogen.  It  can  now  be  obtained  of  high 
purity. 

Sodium  Hydroxid  Solution. — The  white  granulated 
caustic  soda  sold  for  household  use  will  answer;  350  grams 
are  dissolved  in  water  and  made  up  to  1000  c.c. 

Sodium  Carbonate  and  Hydroxid  Solution. — Twenty-five 
grams  of  each  are  dissolved  in  250  c.c.  of  distilled  water, 
and  the  solution  boiled  down  to  200  c.c.  to  free  it  from 
ammonium. 
Analytic  Process : 

Determination  of  Nitrogen  Existing  as  Ammonium. — Two 
hundred  c.c.  of  the  water  are  placed  in  a  stoppered  bottle, 
two  c.c.  each  of  the  solutions  of  sodium  carbonate  and 
sodium  hydroxid  added,  the  stopper  inserted,  the  solutions 
mixed,  and  allowed  to  stand  for  an  hour  or  twro.  A  filter 
is  prepared  by  inserting  a  rather  large  plug  of  absorbent 
cotton  in  a  funnel.  This  should  be  washed  with  ammo- 
nium-free water  until  the  filtrate  gives  no  color  with  Nessler 
reagent.  The  clear  portion  of  the  sample  is  drawn  off 
with  a  pipet  and  run  through  the  filter,  the  first  portions 
being  rejected,  since  it  is  diluted  by  the  water  retained 
in  the  cotton.  The  filtration  is  rapid,  and  when  100  c.c. 
of  the  liquid  have  passed  through  it,  is  nesslerized.  If 
but  little  ammonium  is  present,  a  narrow  tube  about 
60  centimeters  long  should  be  used  for  observing  the 
color. 

D 


5O  ANALYTIC   OPERATIONS. 

Estimation  of  the  Total  Organic  and  Ammoniacal  Nitro- 
gen.— Five  hundred  c.c.  of  the  water  are  placed  in  a  round- 
bottomed  Bohemian  glass  flask,  ten  c.c.  of  concentrated 
sulfuric  acid  added,  and  a  piece  of  pumice-stone  is  heated 
to  bright  redness  and  dropped  in  while  hot.  The  liquid 
is  boiled  for  an  hour  after  it  is  colorless,  or,  at  least,  quite 
pale  yellow.  The  flask  is  allowed  to  cool,  and  about  250 
c.c.  of  ammonium-free  water  added.  Fifty  c.c.  of  the 
sodium  hydroxid  solution  should  be  placed  in  the  distilling 
apparatus,  about  250  c.c.  of  water  added,  a  piece  of  red- 
hot  pumice-stone  dropped  in,  and  the  liquid  distilled  until 
the  distillate  is  free  from  ammonium.  It  is  best  to  distil 
until  the  retort  contains  not  more  than  TOO  c.c.  The 
sulfuric  acid  solution  is  then  poured  in  slowly  by  means 
of  a  funnel,  the  stem  of  which  touches  the  side  of  the  retort, 
so  that  the  two  liquids  do  not  mingle.  The  stopper  of  the 
retort  is  inserted,  the  liquids  mixed  by  gentle  agitation,  and 
distilled.  If  much  ammonium  is  present,  it  is  advisable 
to  distil  the  first  portion  into  about  ten  c.c.  of  very  dilute 
(i:  1000)  sulfuric  acid,  a  piece  of  glass  tube  being  con- 
nected to  the  condensing  worm  so  that  the  lower  end  dips 
below  the  surface  of  the  liquid.  The  distillates  are  col- 
lected and  nesslerized  in  the  usual  way. 

A  blank  experiment  should  be  made  to  determine  the 
amount  of  ammonium  in  the  sulfuric  acid. 

NITROGEN  AS  NITRATES. 

Solutions  Required: 

A.  H.  Gill  has  subjected  the  various  indirect  methods 
of  estimating  nitrates"  to  comparative  examination,  and 
finds  the  following  method  satisfactory : 


SANITARY   EXAMINATIONS.  51 

Phenoldisuljonic  Acid. — Strong  sulfuric  acid  and  pure 
phenol  are  mixed  in  the  proportion  of  37  grams  of  the 
former  to  3  grams  of  the  latter,  and  heated  for  six  hours 
'in,  not  upon,  the  water-bath.  The  resulting  compound 
usually  solidifies  to  a  white  mass  on  standing,  but  can  be 
easily  liquefied  on  the  water-bath  during  the  evaporation 
of  the  samples  to  be  tested. 

Standard  Potassium  Nitrate. — 0.722  gram  of  potassium 
nitrate,  previously  heated  to  a  temperature  just  sufficient 
to  fuse  it,  are  dissolved  in  water,  and  the  solution  made  up 
to  1000  c.c.  One  c.c.  of  this  solution  will  contain  o.oooi 
gram  of  nitrogen. 
Analytic  Process : 

A  measured  volume  of  the  water  is  evaporated  just  to 
dryness  in  a  porcelain  basin  about  six  centimeters  in  di- 
ameter. One  c.c.  of  the  phe^noldisulfonic  acid  is  added  and 
thoroughly  mixed  with  the  residue  by  means  of  a  glass  rod. 
The  liquid  is  then  diluted  with  about  25  c.c.  of  water, 
ammonium  hydroxid  added  in  excess,  and  the  solution 
made  up  to  50  c.c. 

The  nitrate  converts  the  phenoldisulfonic  acid  into 
picric  acid,  which,  by  the  action  of  the  ammonium  hy- 
droxid, forms  ammonium  picrate;  this  imparts  to  the 
solution  a  yellow  color,  the  intensity  of  which  is  propor- 
tional to  the  amount  present. 

One  c.c.  of  the  standard  solution  of  potassium  nitrate 
is  now  similarly  evaporated  in  a  platinum  basin,  treated  as 
above,  and  made  up  to  50  c.c.  The  color  produced  is 
compared  to  that  given  by  the  water,  and  one  or  the  other 
of  the  solutions  is  diluted  until  the  tints  of  the  two  agree. 


I    UNIVERSITY 


52  ANALYTIC   OPERATIONS. 

The  comparative  volumes  of  the  liquids  furnish  the  neces- 
sary data  for  determining  the  amount  of  nitrate. 

The  results  obtained  by  this  method  are  satisfactory. 
Care  should  be  taken  that  the  same  quantities  of  phenoldi- 
sulfonic  acid  are  used  for  the  water  and  for  the  comparison 
liquid. 

With  subsoil  and  other  waters  probably  containing  much 
nitrates,  10  c.c.  will  be  sufficient;  but  with  river  and  spring 
waters,  25  c.c.  may  be  used.  When  the  organic  matter  is 
sufficient  to  color  the  residue,  it  will  be  well  to  purify  the 
water  by  addition  of  aluminum  hydroxid  and  filtration, 
before  evaporating. 

Chlorin  interferes  with  the  accuracy  of  the  test,  but  Gill 
finds  that  when  not  amounting  to  more  than  20  parts  per 
million  it  does  not  impair  the  practical  value  of  the  results. 
When  greater  than  this,  it  is  best  to  evaporate  in  vacuo 
over  sulfuric  acid.  If  the  chlorin  be  more  than  70  parts 
per  million,  it  should  be  considerably  reduced  by  the 
addition  of  silver  sulfate  which  has  been  ascertained  to  be 
free  from  nitrates.  Nitrites  do  not  influence  the  reaction. 

The  following  is  the  process  for  determining  nitrogen  as 
nitrates  (and  nitrites)  recommended  by  the  Chemical 
Section  of  the  A.  A.  A.  S.  It  depends  upon  conversion  into 
ammonium  by  the  copper-zinc  couple,  and  subsequent 
nesslerizing.  It  is  inferior  to  the  phenoldisulfonic  acid 
method,  both  in  convenience  and  accuracy,  and  does  not 
exclude  the  influence  of  nitrites. 

Take  two  wide-mouth  glass-stoppered  bottles,  each  hold- 
ing 250  c.c.,  and  a  piece  of  sheet  zinc  as  long  and  about  as 
wide  as  the  bottles  are  deep  from  the  shoulder  down ;  clean 
the  zinc  by  dipping  in  dilute  acid  and  washing  with  water, 


SANITARY   EXAMINATIONS.  53 

and  make  it  into  a  loose  coil  by  rolling  it  around  a  piece  of 
glass  tube.  Immerse  it  in  a  1.4  to  1.8  per  cent,  solution 
of  copper  sulfate  in  ammonium-free  water,  and  leave  it 
there  until  its  surface  is  well  covered  with  a  continuous 
layer  of  the  black  copper;  lift  it  out  carefully,  cover  it  in 
a  beaker  with  successive  portions  of  ammonium-free  water, 
lifting  it  out  and  draining  each  time,  and  at  once  put  it  into 
one  of  the  bottles  of  acidified  water,  prepared  as  follows: 
Make  500  c.c.  of  the  water  to  be  examined  distinctly 
acid  with  oxalic  acid  added  in  fine  powder,  with  constant 
stirring,  so  that  it  shall  dissolve  readily,  and  pour  half  of 
the  liquid  into  one  of  these  250  c.c.  bottles,  and  half  into 
the  other,  and  leave  them,  stoppered,  in  a  warm  place  for 
twenty-four  hours.  Then  nesslerize  both  samples,  decant- 
ing off  the  portions,  as  wanted,  from  the  precipitated  earthy 
oxalates,  and  using  double  the  usual  quantity  of  Nessler's 
solution,  since  the  free  oxalic  acid  must  be  neutralized 
first  by  the  alkali  of  the  reagent.  The  proportion  of  am- 
monia may  often  be  so  large  in  the  water  in  which  the 
reduction  is  made,  by  the  copper-zinc  couple,  that  only 
five  or  ten  c.c.  can  be  taken  for  each  test,  and  made  up 
to  50  c.c.  by  the  addition  of  ammonium-free  water.  The 
difference  between  the  results  with  the  two  portions  of 
water  gives  the  amount  of  nitrogen  due  to  the  oxidized 
nitrogen  compounds  in  the  water  examined. 

NITROGEN  AS  NITRITES. 

The  following  is  Ilosvay's  modification  of  Griess's  test. 
It  has  the  advantage  over  the  original  method,  that  the 
color  is  developed  more  rapidly,  and  the  solutions  are  less 
liable  to  change. 


54  ANALYTIC   OPERATIONS. 

Solutions  Required: 

i-4-amidobenzenesulfonic  Acid  Solution  (Suljanilic  Acid). 
— Dissolve  0.5  gram  in  150  c.c.  of  diluted  acetic  acid, 
sp.  gr.  1.04. 

a-amidonaphthalene  Acetate  Solution. — Boil  o.i  -gram  of 
solid  a-amidonaphthalene  («-naphthylamin)  in  20  c.c.  of 
water,  filter  the  solution  through  a  plug  of  washed  absor- 
bent cotton,  and  mix  the  filtrate  with  180  c.c.  of  diluted 
acetic  acid.  All  water  used  must  be  free  from  nitrites,  and 
all  vessels  must  be  rinsed  out  with  such  water  before  tests 
are  applied,  since  appreciable  quantities  of  nitrites  may 
be  taken  up  from  the  air. 

Standard  Sodium  Nitrite. — 0.275  gram  pure  silver  nitrite 
is  dissolved  in  pure  water,  and  a  dilute  solution  of  pure 
sodium  chlorid  added  until  the  precipitate  ceases  to  form. 
It  is  then  diluted  with  pure  water  to  250  c.c.,  and  allowed 
to  stand  until  clear.  For  use  10  c.c.  of  this  solution  are 
diluted  to  100  c.c.  It  is  to  be  kept  in  the  dark.  One  c.c. 
of  the  dilute  solution  is  equivalent  to  o.ooooi  gram  nitrogen. 

The  silver  nitrite  is  prepared  thus:  A  hot  concentrated 
solution  of  silver  nitrate  is  added  to  a  concentrated  solu- 
tion of  the  purest  sodium  or  potassium  nitrite  available, 
filtered  while  hot,  and  allowed  to  cool.  The  silver  nitrite 
will  separate  in  fine,  needle-like  crystals,  which  are  freed 
from  the  mother  liquor  by  filtration  by  the  aid  of  a  filter 
pump.  The  crystals  are  dissolved  in  the  smallest  possible 
quantity  of  hot  water,  allowed  to  cool,  and  again  separated 
by  means  of  the  pump.  They  are  then  thoroughly  dried 
in  the  water-bath,  and  preserved  in  a  tightly  stoppered 
bottle  away  from  the  light.  The  purity  may  be  tested  by 
heating  a  weighed  quantity  to  redness  in  a  tared  porcelain 


SANITARY   EXAMINATIONS.  55 

crucible  and  noting  the  weight  of  the  metallic  silver.     One 
hundred   and   fifty-four  parts   should   leave   a   residue   of 
1 08  parts  silver. 
Analytic  Process : 

Twenty-five  c.c.  of  the  water  are  placed  in  one  of  the 
color-comparison  cylinders,  and  two  c.c.  each  of  the  test 
solutions  are  dropped  in.  It  is  convenient  to  have  a  pipet 
for  each  solution,  and  to  use  it  for  no  other  purpose. 

One  c.c.  of  the  standard  nitrite  solution  is  placed  in 
another  clean  cylinder,  made  up  with  nitrite-free  water  to 
25  c.c.  and  treated  with  the  reagents  as  above. 

In  the  presence  of  nitrites  a  pink  color  is  produced.  At 
the  end  of  five  minutes  the  two  solutions  are  compared, 
the  colors  equalized  by  diluting  the  darker,  and  the  calcu- 
lation made  as  explained  under  the  estimation  of  nitrates. 

The  reactions  consist  in  tjie  conversion  of  the  sulfanilic 
acid  into  diazobenzenesulfonic  anhydrid,  by  the  nitrite 
present;  this  compound  is  then  in  turn  converted  by  the 
amidonaphthalene  into  azo-a-amidonaphthalene-i-4-ben- 
zenesulfonic  acid.  The  last-named  body  gives  the  color 
to  the  liquid. 

OXYGEN-CONSUMING  POWER. 

All  organic  materials  being  more  or  less  easily  oxidized, 
several  methods  have  been  suggested  for  determining  the 
oxygen-consuming  powers  of  waters  by  treatment  with 
active  oxidizing  agents.  These  methods  are,  however, 
limited  in  value.  The  organic  matters  in  water  differ 
much  in  character  and  condition,  and  their  oxidability  is 
subject  to  much  variation,  according  to  the  circumstances 
under  which  the  test  is  made.  Nevertheless,  as  a  high 


56  ANALYTIC   OPERATIONS. 

oxygen-consuming  power  certainly  indicates  departure 
from  purity,  some  additional  evidence  may  be  obtained. 
Potassium  permanganate  is  especially  suitable.  The  test  is 
usually  made  by  introducing  a  known  amount  of  the  per- 
manganate into  the  water,  which  has  been  rendered  acid, 
and  measuring  after  a  definite  period  the  proportion  which 
has  been  decomposed. 

It  must  not  be  overlooked  that  if  a  water  contains  nitrites, 
ferrous  compounds,  or  sulfur  compounds  other  than  sul- 
fates,  the  proportion  of  oxygen  consumed  will  be  greater 
than  that  required  for  the  organic  matter.  It  has  been 
proposed,  in  order  to  remove  the  nitrites  before  applying 
the  permanganate,  to  take  500  c.c.  of  the  water,  add  10  c.c. 
of  the  dilute  sulfuric  acid,  boil  for  twenty  minutes,  allow 
to  cool,  and  then  treat  with  permanganate.  Since,  how- 
ever, the  amount  of  nitrites,  if  appreciable,  can  be  directly 
determined,  it  is  more  satisfactory  to  deduct  from  the 
oxygen  consumed  the  amount  required  to  convert  the 
nitrites  present  into  nitrates,  and  the  remainder  will  be 
that  required  for  the  other  oxidizable  ingredients.  Four- 
teen parts  of  nitrogen  existing  as  nitrite  require  16  parts 
of  oxygen  for  conversion  into  nitrate.  Similarly,  112 
parts  of  iron  in  a  ferrous  compound  will  require  16  parts 
of  oxygen  for  conversion  to  the  ferric  condition. 

Of  the  following  methods  the  first  is  due,  in  the  main, 
to  Tidy,  has  been  improved  by  Dupre,  and  was  approved 
by  the  Society  of  Public  Analysts  of  Great  Britain : 
Solutions  Required : 

Standard  Permanganate. — 0.395  gram  pure  potassium 
permanganate  is  dissolved  in  distilled  water,  and  the 


SANITARY   EXAMINATIONS.  57 

solution  made  up  to  1000  c.c.     One  c.c.  is  equal  to  o.oooi 
gram  oxygen. 

Diluted  Suljuric  Acid. — Add  50  c.c.  of  pure  sulfuric 
acid  to  100  c.c.  of  water,  and  then  add  solution  of  potas- 
sium permanganate  until  a  faint  pink  color  is  obtained, 
which  is  permanent  when  the  liquid  is  heated  to  80°  F. 
for  four  hours. 

Potassium  lodid. — Ten  grams  of  the  pure  salt  recrystal- 
lized  from  alcohol  are  dissolved  in  100  c.c.  of  distilled  water. 

Sodium  Thiosuljate. — One  gram  of  the  pure  crystallized 
salt  dissolved  in  2000  c.c.  of  distilled  water. 

Starch  Indicator. — One  gram  of  clean  starch  is  mixed 
smoothly  with  cold  water  into  a  thin  paste,  then  poured 
gradually  into  about  200  c.c.  of  boiling  water,  the  boiling 
continued  for  one  minute,  the  liquid  allowed  to-  settle,  and 
the  clear  portion  used.  It  js  best  freshly  prepared. 
Analytic  Process : 

Two  determinations  are  made — one,  of  the  oxygen  con- 
sumed in  fifteen  minutes,  which  is  considered  to  represent 
the  nitrites,  sulfids,  or  ferrous  compounds,  and  the  other, 
of  the  oxygen  consumed  by  four  hours'  action.  Both  de- 
terminations are  made  at  a  temperature  of  80°  F.  Three 
glass-stoppered  bottles,  of  about  350  c.c.  capacity,  are 
rinsed  with  strong  sulfuric  acid  and  then  with  water.  In 
one  is  placed  250  c.c.  of  pure  distilled  water  as  a  control 
experiment,  and  in  each  of  the  others  250  c.c.  of  the  water 
to  be  tested.  The  bottles  are  stoppered  and  brought  to  a 
temperature  of  80°  F.;  10  c.c.  of  the  dilute  sulfuric  acid 
and  10  c.c.  of  the  standard  permanganate  are  added  to 
each,  and  the  stoppers  again  replaced.  At  the  end  of 
fifteen  minutes  one  sample  of  water  is  removed  from  the 


58  ANALYTIC   OPERATIONS. 

bath,  and  two  or  three  drops  of  the  potassium  iodid  solu- 
tion added  to  remove  the  pink  color.  After  thorough 
admixture,  the  thiosulfate  solution  is  run  in  from  a  buret 
until  the  yellow  color  is  nearly  destroyed,  a  few  drops  of 
the  starch  solution  added,  and  the  addition  of  the  thiosul- 
fate continued  until  the  blue  color  is  quite  discharged. 
If  the  addition  of  the  thiosulfate  solution  has  been  properly 
conducted,  one  drop  of  the  permanganate  solution  will 
restore  the  blue  color. 

The  other  bottles  are  maintained  at  80°  F.  for  four 
hours.  Should  the  pink  color  disappear  rapidly  in  the 
bottle  containing  the  water  under  examination,  10  c.c.  of 
the  permanganate  solution  must  be  added  to  each  bottle, 
in  order  to  maintain  a  distinct  pink  color.  At  the  end  of 
four  hours  each  bottle  is  removed  from  the  bath,  two 
or  three  drops  of  potassium  iodid  added,  and  the  titration 
with  thiosulfate  solution  conducted  as  just  described. 
The  calculation  is  most  conveniently  made  as  follows: 

a  =  number  of  c.c.  required  for  the  control  experiment. 
b  =  number  of  c.c.  required  for  the  water  under  examina- 
tion. 

c  =  available  O  in  permanganate  (o.ooi  for  10  c.c.). 
x  =  oxygen  consumed  by  water. 
Then,  a  :  a-b  :  :  c  :  x. 

The  following  method  was  recommended  by  the  Chemical 
Section  of  the  American  Association  for  the  Advancement 
of  Science: 

"Prepare  a  solution  of  potassium  permanganate  con- 
taining 0.2  milligram  of  available  oxygen  to  i  c.c.  and  a 


SANITARY   EXAMINATIONS.  59 

solution  of  oxalic  acid  of  such  strength  as  to  decompose 
the  permanganate  solution,  volume  for  volume,  the  strength 
being  redetermined  from  time  to  time.  The  water  used 
for  making. these  solutions  should  be  purified  by  distillation 
from  alkaline  permanganate. 

"To  200  c.c.  of  water  to  be  examined,  in  a  400  c.c.  flask, 
add  10  c.c.  of  dilute  sulfuric  acid  (1:3)  and  such  measured 
quantity  of  the  permanganate  as  will  give  a  persistent 
color;  boil  ten  minutes,  add,  if  necessary,  more  perman- 
ganate in  measured  quantities,  so  as  to  maintain  the  red 
color;  remove  the  flask  from  the  lamp,  add  10  c.c.  of  oxalic 
acid  solution  to  destroy  the  color,  or  more  if  required  by 
the  excess  of  permanganate,  and  then  add  permanganate, 
drop  by  drop,  until  a  faint  pink  tint  appears..  From  the 
total  quantity  of  permanganate  used  deduct  the  equivalent 
of  the  oxalic  acid  used,  and,  from  the  remainder  calculate 
the  milligrams  of  oxygen  consumed  by  the  oxidizable 
organic  matter  in  the  water." 

The  oxygen-consuming  power  may  also  be  indirectly 
estimated  by  the  action  of  the  organic  matter  upon  silver 
compounds.  H.  Fleck's  method  depends  upon  the  reduc- 
tion produced  by  boiling  the  water  with  alkaline  solution 
of  silver  thiosulfate  and  estimation  of  the  unreduced  silver. 
A.  R.  Leeds  has  proposed  a  method  by  treating  the  water 
with  decinormal  silver  nitrate,  exposing  to  light  until  it 
settles  perfectly  clear,  and  estimating  the  reduced  silver. 

These  methods  are  open  to  practically  the  same  objec- 
tions as  in  the  use  of  permanganate,  and  do  not  seem  to 
possess  any  decided  advantage.  Qualitative  results  of 
some  interest  may  occasionally  be  obtained  by  the  fol- 
lowing method:  Two  c.c.  of  a  one  per  cent,  solution  of 


60  ANALYTIC   OPERATIONS. 

silver  nitrate,  rendered  decidedly  alkaline  by  ammonium 
hydroxid,  are  added  to  100  c.c.  of  the  water  in  a  stoppered 
bottle,  which  is  then  placed  in  full  sunlight  for  two  hours. 
Waters  containing  but  little  organic  matter  will  not  show 
at  the  end  of  this  period  any  appreciable  tint. 

PHOSPHATES. 

The  following  method  is  recommended  by  A.  G.  Wood- 
man: 
Solutions  Required : 

Ammonium  Molybdate  Solution. — 50  grams  in  i  liter  of 
distilled  water. 

Nitric  acid,  sp.  gr.  107. 

Sodium   Phosphate  Solution. — 0.5324  gram   crystallized 
disodium  hydrogen  phosphate,  100  c.c.  of  the  above  nitric 
acid,  distilled  water  sufficient  to  make   i   liter.     This  is 
equivalent  to  o.oooi  P2O5  in  i  c.c. 
Analytic  Process : 

Fifty  c.c.  of  the  sample  and  3  c.c.  of  nitric  acid  are  eva- 
porated to  dryness  in  a  porcelain  dish  on  the  water-bath, 
the  residue  heated  for  two  hours  at  100°  C.,  and  treated 
with  50  c.c.  of  cold  distilled  water  added  in  several  portions 
which  are  mixed  in  a  comparison  tube.  It  is  usually  un- 
necessary to  filter.  Four  c.c.  of  the  ammonium  molybdate 
solution  and  2  c.c.  of  nitric  acid  are  added,  the  contents 
mixed,  and  after  three  minutes  the  color  compared  with 
that  given  by  different  quantities  of  the  standard  phos- 
phate solution  which  have  been  made  up  to  50  c.c.  and  the 
reagents  added  in  the  same  amount  as  above. 

Blank  tests  must  be  made  to  determine  the  purity  of  the 
materials  used.  Distilled  water  kept  for  some  time  in 


SANITARY   EXAMINATIONS.  6 1 

glass  vessels  may  contain  appreciable  amounts  of  substances 
giving  color  with  the  reagents. 

Ammonium  molybdate  solution  suitable  for  the  gravi- 
metric determination  of  phosphates  may  be  prepared  as 
follows : 

Weigh  into  a  beaker  10  grams  of  pure  molybdenum  ter- 
oxid,  mix  well  with  40  c.c.  cold  distilled  water,  and  add 
8  c.c.  strong  ammonium  hydroxid,  sp.  gr.  0.900.  When 
completely  dissolved,  filter  and  pour  slowly,  with  constant 
stirring,  into  a  mixture  of  40  c.c.  of  nitric  acid,  sp.  gr. 
1.42,  and  60  c.c.  of  water.  Add  0.005  gram  sodium  am- 
monium hydrogen  phosphate,  dissolved  in  a  little  water, 
agitate  well,  allow  precipitate  to  settle  twenty-four  hours, 
and  filter  before  using. 

DISSOLVED  OXYGEN. 

The  method  here  given,  a  modification  of  Mohr's,  was 
proposed  by  Blarez.     It  is  rapid  and  satisfactory. 
Solutions  Required : 

Sodium  Hydroxid. — Forty  grams  of  pure  sodium  hy- 
droxid  to  the  liter. 

Ferrous-ammonium  Sulfate. — Forty  grams  dissolved-  in 
about  a  liter  of  water,  and  acidified  with  a  few  drops  of 
concentrated  sulfuric  acid. 

Decinormal  Potassium  Permanganate. — 3.156  grams  dis- 
solved in  a  liter  of  distilled  water.  The  accuracy  of  this 
solution  should  be  determined  by  titration  with  a  known 
weight  of  ferrous-ammonium  sulfate.  One  c.c.  should  be 
equivalent  to  0.0392  gram  ferrous  ammonium  sulfate 
(0.0008  gram  of  oxygen). 


62 


ANALYTIC    OPERATIONS. 


The  apparatus  employed  (shown  in  Fig.  12)  is  a  globular 
separator,  of  about  250  c.c.  capacity.  Above  the  bulb  is  a 
caoutchouc  stopper  carrying  a  cylindric  funnel,  of  about 
12  c.c.  capacity,  terminating  in  a  tube,  8  mm.  caliber, 
sharply  contracted  at  the  outlet  to  a  capillary  opening. 
The  tube  should  project  about  6  mm.  below  the  stopper. 
The  exact  capacity  of  the  apparatus  is  measured  as  follows : 
The  bulb  is  completely  filled  with  water  and  the  stopper 
inserted;  the  level  of  the  water  will  rise  slightly  in  the 
funnel  tube,  and  should  be  brought  down  to  its 
outlet  by  drawing  a  little  off  at  the  stop-cock, 
after  which  the  water  is  run  into  a  graduated 
measure  and  its  volume  noted. 
Analytic  Process : 

Thirty-five  c.c.  of  mercury  and  ten  c.c.  of 
sodium  hydroxid  solution  are  put  into  the  bulb, 
and  then  sufficient  of  the  water  to  be  tested  to 
fill  it.  The  funnel  stopper  is  inserted,  and  the 
water  which  rises  into  the  funnel  brought  into 
the  bulb  by  cautiously  running  out  at  the  stop- 
cock, mercury,  the  volume  of  which  should  be 
noted.  The  exact  volume  of  water  used  is  thus 
known.  Five  c.c.  of  the  ferrous  ammonium  sulfate  solution 
are  poured  into  the  funnel,  brought  into  the  bulb  by  running 
out  mercury,  and  the  liquid  thoroughly  mixed  by  giving  the 
apparatus  a  gyratory  movement.  After  standing  five  or  six 
minutes,  the  oxygen  will  be  completely  absorbed;  10  c.c.  of 
the  diluted  sulfuric  acid  are  now  added  by  the  same  method. 
On  agitating  the  bulb,  the  contents  become  clear.  The 
watery  liquid  is  then  transferred  to  a  beaker  and  titrated 
with  decinormal  permanganate.  A  volume  of  water  equal 


FIG.  12. 


SANITARY   EXAMINATIONS.  63 

to  that  used  in  the  test  is  poured  into  another  beaker,  10 
c.c.  each  of  the  sodium  hydro xid  and  diluted  sulfuric  acid 
added,  and  then  5  c.c.  of  ferrous  ammonium  sulfate  solu- 
tion. The  resulting  liquid  is  titrated  with  permanganate. 
The  weight  of  oxygen  corresponding  to  the  difference  be- 
tween the  two  titrations  gives  the  weight  of  dissolved  oxygen 
in  the  liquid  employed. 

Nitrates  do  not  appear  to  impair  the  accuracy  of  this 
method,  and  the  interfering  action  of  nitrites  and  other 
reducing  compounds  is  avoided  by  the  control  experiment. 

It  is  perhaps  hardly  necessary  to  add  that  the  exact  tem- 
perature of  the  water  is  to  be  noted  at  the  time  of  collection 
of  the  sample. 

In  transferring  to  the  bulb,  the  water  should  be  agitated 
as  little  as  possible  in  contact  with  the  air,  in  order  to 
avoid  the  absorption  of  oxygen.  A  siphon  should  be  used 
for  this  purpose,  the  lower  end  being  allowed  to  reach  to 
the  bottom  of  the  bulb. 

POISONOUS  METALS. 

Under  this  conventional  title  are  included  barium, 
chromium,  zinc,  arsenic,  copper,  and  lead;  manganese,  iron, 
aluminum,  also,  though  not  usually  classed  in  this  group, 
are  objectionable  when  present  in  notable  amounts. 
''  Barium  is  rarely  present,  and  only  in  water  containing 
no  sulfates.  It  can  be  detected  and  estimated  by  slightly 
acidifying  the  water  with  hydrochloric  acid,  filtering  if 
necessary,  and  addihg  solution  of  calcium  sulfate.  The 
precipitated  barium  sulfate  is  collected  and  weighed  in 
the  usual  way. 

Chromium  is  rarely  present,  but  may  be  looked  for  in 


64  ANALYTIC   OPERATIONS. 

the  waste  waters  of  dye-works  and  similar  sources.  To 
detect  it,  a  considerable  volume  of  the  water  is  evaporated 
to  dryness  with  addition  of  a  small  amount  of  potassium 
chlorate  and  nitrate,  transferred  to  a  porcelain  crucible  and 
brought  to  quiet  fusion;  any  chromium  present  will  be 
found  in  the  residue  in  the  form  of  chromate.  The  fused 
mass,  after  cooling,  is  boiled  with  a  little  water,  filtered, 
the  filtrate  rendered  slightly  acid  with  hydrochloric  acid, 
and  a  solution  of  hydrogen  dioxid  added.  In  the  presence 
of  chromium  a  transient  blue  color  will  appear;  by  adding 
a  little  ether  and  shaking  the  mixture,  the  color  will  pass 
into  the  ether,  and  on  standing  will  form  a  blue  layer  on  the 
surface  of  the  water. 

Zinc  is  best  detected  by  the  test  described  by  Allen. 
The  water  is  rendered  slightly  alkaline  by  addition  of 
ammonium  hydroxid,  heated  to  boiling,  filtered,  and  the 
clear  liquid  treated  with  a  few  drops  of  potassium  ferro- 
cyanid;  in  the  presence  even  of  the  merest  trace  of  zinc 
a  white  precipitate  will  be  produced, 
v  Arsenic  is  most  readily  detected  by  Reinsch's  test. 
One  liter  of  the  water  is  rendered  slightly  alkaline  by  pure 
sodium  carbonate,  and  evaporated  nearly  to  dryness  in  a 
porcelain  basin.  Two  or  three  c.c.  of  water  strongly  acidu- 
lated with  hydrochloric  acid  are  placed  in  a  small  test-tube, 
about  J  of  a  square  centimeter  of  bright  copper  foil  is 
added,  and  the  liquid  boiled  gently  for  a  few  moments.  If 
the  copper  remains  bright,  showing  that  the  reagents  con- 
tain no  arsenic,  the  water-residue  is  acidified  with  hydro- 
chloric acid,  added  to  the  contents  of  the  test-tube,  and  the 
liquid  again  boiled  for  several  minutes.  If  arsenic  be  pres- 
ent, a  steel-gray  stain  will  appear  on  the  copper.  The  slip 


SANITARY  EXAMINATIONS.  65 

is  removed,  washed  with  distilled  water,  thoroughly  dried  by 
pressure  between  filter  paper,  inserted  into  a  narrow  glass 
tube  closed  at  one  end,  which  has  been  previously  dried  by 
heating  nearly  to  redness.  The  tube  is  gently  heated  at 
the  point  at  which  the  copper  rests ;  the  deposit  will  sublime 
and  collect  on  the  cooler  portion  of  the  tube,  in  crystals 
which  the  microscope  shows  to  be  octahedral. 

Since  small  amounts  of  arsenic  frequently  occur  in  re- 
agents and  in  glass  vessels,  care  must  be  taken  to  avoid 
such  sources  of  error.  Sodium  carbonate  solution  may 
contain  arsenic  dissolved  from  the  glass  bottle  in  which 
it  is  kept.  It  is  best,  therefore,  to  use  the  solid  carbonate 
for  rendering  the  water  alkaline,  and  to  determine  its 
purity  before  use. 

/  Iron  is  detected  by  the  addition  of  a  drop  of  ammonium 

I  sulfid  to  the  water  in  a  tall^  glass  cylinder.     Ferrous  sul- 

(    fid    is    formed,    having    a   greenish-black    color,    instantly 

,    discharged  by  acidifying  the  water  with  dilute  hydrochloric 

|  acid.     A  still  better  test  is  the  production  of  a  blood-red 

(  color,  with  potassium  thiocyanate,  due  to  the  formation 

1   of  ferric  thiocyanate.     The  water  should  be  first  boiled 

with  a  few  drops  of  nitric  acid,  to  convert  the  iron  to  the 

1    ferric  condition,  cooled,  and  a  drop  or  two  of  the  solution 

I   of  potassium  thiocyanate  added.     The  test  is  very  delicate. 

Either  of  the  above  tests  may  be  made  quantitative  by 

matching  the  color  produced  in  100  c.c.  of  the  water  with 

that  obtained  from  a  known  weight  of  iron.     The  method 

with  potassium  thiocyanate  is  preferable,   as  it  is  more 

delicate  and  there  are  fewer  interfering  conditions.     The 

following  is  the  method  as  elaborated  by  Thompson  and 

described  in   Sutton's   "Volumetric  Analysis": 


66  ANALYTIC   OPERATIONS. 

Solutions  Required: 

Standard  Ferric  Suljate. — 0.7  gram  ferrous  ammonium 
sulfate  is  dissolved  in  water  acidified  with  sulfuric  acid, 
and  potassium  permanganate  solution  added  until  the 
solution  turns  a  very  faint  pink  color.  The  solution  is 
diluted  to  a  liter.  One  c.c.  contains  o.i  milligram  iron. 

Diluted  Nitric  Acid. — Thirty  c.c.  concentrated  nitric 
acid  diluted  with  water  to  about  100  c.c. 

Potassium   Thiocyanate. — Five  grams  of   the    salt    dis- 
solved in  about  100  c.c.  water. 
Analytic  Process : 

About  100  c.c.  of  the  water  are  evaporated  to  small  bulk, 
acidified  with  hydrochloric  acid,,  and  just  sufficient  dilute 
potassium  permanganate  solution  added  to  convert  all  the 
iron  to  the  ferric  condition.  The  liquid  is  evaporated 
nearly  to  dryness  to  drive  off  excess  of  acid,  then  diluted 
to  its  original  volume,  100  c.c.  In  two  tall  glasses  marked 
at  100  c.c.,  5  c.c.  of  the  nitric  acid  and  15  c.c.  of  the  thio- 
cyanate  solution  are  placed.  To  one  of  these  a  measured 
volume  of  the  treated  water  is  added  and  both  vessels 
filled  up  to  the  mark  with  distilled  water.  If  iron  is  present, 
a  blood-red  color  will  be  produced.  Standard  iron  solu- 
tion is  added  to  the  second  vessel  until  the  color  agrees. 
The  amount  of  water  which  is  added  to  the  first  glass  will 
depend  upon  the  quantity  of  iron  it  contains;  not  more 
should  be  used  than  will  require  two  or  three  c.c.  of  the 
standard  to  match  it,  otherwise  the  color  will  be  too  deep 
for  comparison. 

Manganese.— The  following  method  is  described  by 
Wanklyn  in  his  treatise  on  water  analysis.  About  one  liter 
of  the  water  is  evaporated  to  small  bulk,  nearly  neutralized 


SANITARY  EXAMINATIONS.  67 

by  hydrochloric  acid  and  treated  with  a  few  drops  of  a 
solution  of  hydrogen  dioxid.  The  formation  of  a  brown 
precipitate  indicates  the  presence  of  manganese.  The  test 
is  very  delicate.  The  precipitate  may  be  collected  on 
a  filter,  the  filter  ashed,  and  the  residue  fused  with  a  mix- 
ture of  sodium  carbonate  and  potassium  nitrate.  Green 
potassium  manganate  will  be  produced,  which,  when  boiled 
with  water,  will  give  a  bright-red  solution  of  potassium 
permanganate.  The  quantitative  determination  is  given 
elsewhere. 

Aluminum. — Traces  of  this  element  are  to  be  ex- 
pected in  all  waters,  and  it  is  not  usual  to  test  for  it  except 
in  elaborate  analysis  of  the  mineral  ingredients,  as  de- 
scribed in  another  section.  The  use  of  aluminum  sulfate 
as  a  coagulant  in  many  rapid-filtration  methods  makes  it 
necessary  to  examine  effluen-ts  for  excess  of  precipitant,  and 
this  may  be  done  by  the  following  method  devised  by 
Mrs.  Richards: 

To  25  c.c.  of  the  water  to  be  tested  (concentrated  from 
one  liter  or  more,  if  necessary)  is  added  a  few  drops  of 
freshly  prepared  logwood  decoction;  any  alkali  is  neutral- 
ized and  the  color  is  brightened  by  the  addition  of  two 
or  three  drops  of  acetic  acid.  By  comparison  with  standard 
solutions,  the  amount  of  alum  present  may  be  determined. 
One  part  of  alum  in  1,000,000  of  water  can  be  detected 
with  certainty.  In  cases  of  greater  dilution,  concentration 
of  several  liters  may  be  necessary  to  obtain  a  decisive 
test.  The  logwood  chips  yield  the  right  color  only  after 
having  been  treated  with  boiling  water  two  or  three  times, 
rejecting  the  successive  decoctions.  The  first  portion  gives 
a  yellow  color,  the  third  or  fourth  usually  a  deep  red.  The 
logwood  chips  must  be  fresh. 


68  ANALYTIC   OPERATIONS. 

f    Lead  may  be  readily  detected  by  adding  to  the  water  in 
'  a  tall  glass  cylinder  a  drop  of  ammonium  sulfid;  brown  - 
(   ish-black  lead  sulfid  is  formed,   which  does  not  dissolve 
(    either  by  acidulating  the  water  with  dilute  hydrochloric 
'.    acid  (distinction  from  iron),  nor  by  the  addition  of  about 
'    one  c.c.  of  a  strong  solution  of  potassium  cyanid  (distinction 
'    from    copper).     S.    Harvey   gives   the    following    method: 
250  c.c.  are  placed  in  a  precipitating  jar,  about  o.i  gram 
of   crystallized   potassium   dichromate   is   added   and   dis- 
solved by  agitation.     The  same  volume  of  lead-free  water 
is  treated  in  the  same  manner,  and  the  two  solutions  placed 
side  by  side.     Water  containing  0.3  part  per  million  will 
show  a  turbidity  in  fifteen  minutes  which  will  be  rendered 
more  distinct  by  contrast  with  the  clear  water  alongside. 
By  allowing  the  jar  to  stand  for  about  twelve  hours  un- 
disturbed, the  precipitate  will  settle  and  will  become  still 
more   distinct.     No  other   metal   likely  to   be   present   in 
water  will  give  a  similar  reaction. 

In  the  absence  of  copper  the  amount  of  lead  present  may 
be  determined  as  follows :  A  solution  is  prepared  containing 
1.6  grams  of  lead  nitrate  to  the  liter;  one  c.c.  of  this  contains 
one  milligram  lead.  One  hundred  c.c.  of  the  water  to  be 
tested  are  placed  in  a  tall  glass  vessel,  made  acid  by  the 
addition  of  a  few  drops  of  acetic  acid,  and  five  c.c.  of  hy- 
drogen sulfid  added.  In  a  similar  vessel  100  c.c.  of  dis- 
tilled water  are  placed,  together  with  the  same  quantities  of 
acetic  acid  and  hydrogen  sulfid,  and  sufficient  of  the  stan- 
dard lead  solution  to  match  the  tint  in  the  first  cylinder. 
The  amount  of  lead  in  the  water  under  examination  is  thus 
known. 

Copper  is  detected  in  the  same  manner  as  lead  by  acidify- 


SANITARY   EXAMINATIONS.  69 

ing  the  water  with  acetic  acid  and  adding  hydrogen  sulfid. 
The  precipitate  is  distinguished  from  lead  sulfid  by  the 
fact  that  the  color  is  discharged  on  the  addition  of  about 
i  c.c.  of  a  strong  solution  of  pure  potassium  cyanid.  It 
may  be  further  confirmed  by  the  addition  to  another  por- 
tion of  the  water  of  a  solution  of  potassium  ferrocyanid. 
In  the  presence  of  even  a  very  small  amount  of  copper,  a 
mahogany-red  color  is  produced. 

In  the  absence  of  lead,  copper  is  estimated  in  the  same 
way  as  that  metal,  using,  however,  a  standard  solution  of 
copper  for  the  comparison  liquid.  This  is  made  by  dis- 
solving 3.929  grams  of  crystallized  copper  sulfate  in  one 
liter  of  water.  One  c.c.  of  the  solution  contains  one  milli- 
gram copper. 

If  both  lead  and  copper  are  present,  a  large  quantity  of 
the  water  should  be  evaporated  to  small  bulk,  and  the 
metals  separated  and  estimated  by  any  one  of  the  ordinary 
laboratory  methods. 

BIOLOGIC  EXAMINATIONS. 

In  a  comprehensive  sense  the  living  organisms  of  water 
include  representatives  of  all  the  great  groups  of  animals 
and  plants.  The  higher  orders  of  organic  forms  are  absent 
from  very  foul  water.  From  an  analytic  point  of  view, 
observation  is  limited  to  the  determinations  of  those  forms 
which  are  inappreciable  to  the  unassisted  eye.  So  far  as 
regards  some  of  the  moderately  complex  organisms,  such 
as  the  minute  crustaceans,  algae,  desmids,  and  even  the 
amebse,  it  may  be  said  that  while  some  general  inferences 
as  to  the  character  and  history  of  the  water  may  be  deduced 
from  an  identification  of  the  specific  forms,  no  definite 


70  ANALYTIC   OPERATIONS. 

sanitary  signification  can  be  attached  to  them.  From 
what  is  now  known  of  the  life-history  of  many  parasitic' 
organisms,  it  is  evident  that  water  that  is  freely  accessible 
to  any  animal  forms  is  liable  to  be  dangerously  polluted. 
Moreover,  the  dead  bodies  of  such  animals  will  furnish 
food  to  many  forms  of  microbes  and  thus  assist  in  the 
multiplication  of  the  latter.  The  ova  of  the  entozoa  might 
in  some  cases  be  detected  by  careful  search,  and  would 
indicate  recent  pollution  of  a  highly  dangerous  character 

The  number  of  the  higher  forms  present  in  any  sample 
will  depend  very  much  upon  the  point  at  which  it  is  col- 
lected, they  being  more  numerous  in  the  neighborhood  of 
large  plants  and  at  the  bottom  and  sides  of  streams. 

Several  observers,  notably  Sedgwick  and  Rafter,  have 
paid  considerable  attention  to  the  recognition  of  the  animal 
and  vegetable  forms  in  surface  waters.  Some  of  these 
forms  cause  disagreeable  odors  and  colors;  in  the  warm 
season  of  the  year,  when  such  water  is  stored  in  reservoirs, 
considerable  annoyance  is  felt  by  the  users,  and  the 
engineer-in-charge  is  subjected  to  much  criticism.  It  has 
been  found  that  even  crude  nitration  methods,  such  as  allow- 
ing the  water  to  pass  through  a  dike  of  porous  soil  before 
storing  it  in  a  reservoir,  will  diminish  the  tendency  to  these 
conditions.  Cleansing  a  reservoir,  disinfecting  the  inner 
surface,  for  instance,  by  whitewashing,  has  also  improved 
the  condition. 

Observation,  especially  in  Massachusetts,  has  shown 
that  reservoirs  intended  for  even  moderately  prolonged 
storage  of  water  should  be  clean — that  is,,  organic  matter 
of  any  kind  should  not  be  allowed  to  accumulate  on  the 
bottom  and  sides.  Drown  states  that  while  the  water  in 


SANITARY   EXAMINATIONS.  7 1 

one  basin  became  foul  from  stagnation,  in  another  which 
was  carefully  prepared  by  the  removal  of  all  soil  and  vege- 
table matter,  and  is  supplied  by  a  brown,  swampy  water 
from  a  district  almost  entirely  free  from  pollution,  the 
water  is  good  at  a  depth  of  forty  feet. 

In  Philadelphia,  where  large  storage  reservoirs  are  used 
for  water  that  is  often  very  muddy,  but  little  trouble  from 
the  growth  of  microscopic  organisms  occurs.  These  reser- 
voirs are  artificial  basins. 

Sedgwick's  method  of  collecting  organisms  other  than 
microbes,  with  some  modifications  by  Williston,  is  as 
follows : 

In  ordinary  cases  about  100  c.c.  are  employed.  Some- 
times it  will  be  advantageous  to  use  double  this  quantity, 
at  other  times  much  less.  In  rare  cases  the  examination 
can  be  made  upon  unfiltere/l  water.  Originally  sand  was 
employed  for  a  filter  material,  but  Williston  finds  that 
precipitated  silica,  made  by  decomposing  silicon  fluorid 
with  water,  is  more  satisfactory.  This  precipitated  silica 
is  a  commercial  article,  and  its  method  of  preparation  is 
given  in  all  the  larger  manuals  of  chemistry. 

A  small  glass  funnel  with  an  even-calibered  stem  is 
selected,  and  the  lower  end  of  the  stem  plugged  with  a 
little  absorbent  cotton,  upon  which  a  layer  three  or  four 
mm.  deep  of  the  filter-material  is  placed.  The  requisite 
volume  of  water  is  then  allowed  to  filter  through.  The 
pledget  of  cotton  is  removed,  and  the  filter-material  is 
washed  down  with  filtered  or  distilled  water  into  a  cell 
intended  for  microscopic  examination.  This  cell  is  a  glass 
plate  accurately  ruled,  to  which  is  attached  a  brass  cell  50 
mm.  long  by  10  mm.  wide,  of  depth  sufficient  to  hold 


72  ANALYTIC   OPERATIONS. 

about  two  c.c.  of  water.  After  the  material  has  been 
allowed  to  distribute  itself  and  settle  in  the  cell,  it  is  ex- 
amined with  a  moderate  power,  and  the  different  organisms 
in  a  varying  number  of  the  squares  counted.  Each  or- 
ganism may  be  counted  by  itself,  if  occurring  in  large 
numbers,  the  average  of  a  few  squares  being  sufficient  for 
the  purpose.  Organisms  less  numerously  represented  may 
be  counted  by  averaging  a  larger  number  of  squares. 

Filtering  in  this  manner  can  not  be  relied  upon  in  all 
cases.  Indeed,  in  most  cases  the  unfiltered  water  also 
should  be  examined.  Some  of  the  minute  unicellular 
organisms  pass  readily  through  the  small  extent  of  sand  or 
precipitated  silica,  or  even  through  filter-paper. 

It  is  not  unlikely  that  the  high-speed  centrifugal  appara- 
tus now  used  in  laboratories,  associated  with  the  employ- 
ment of  some  fine  precipitant,  will  aid  in  these  investiga- 
tions. 

Dibdin  prepares  as  follows,  a  "micro-filter,"  for  the 
collection  of  minute  suspended  matters:  A  piece  of  com- 
bustion-tubing 20  to  25  cm.  long  is  cleaned  and  drawn 
out  in  the  middle  to  a  capillary  tube,  and  broken  by  a 
file  scratch  at  a  point  at  which  the  caliber  is  not  more  than 
two  millimeters.  Each  of  these  pieces  serves  for  a  filter. 
A  mixture  of  equal  parts  of  air-dried  clay  and  infusorial 
earth  is  made  into  a  smooth,  stiff  paste  with  water  and 
spread  out  on  a  slab  in  a  layer  about  two  millimeters  deep. 
The  capillary  end  of  a  tube  is  pressed  down  into  the  mass 
and  moved  in  a  circle  until  a  plug  is  formed.  This  is 
warmed  until  dry,  and  heated  to  redness,  forming  a  close 
filter. 

The  water  to  be  examined  is  filtered  in  considerable 


SANITARY   EXAMINATIONS.  73 

amount, — one  liter,  for  example,  if  there  is  but  little  sus- 
pended matter, — first  through  a  hardened  paper  filter  placed 
in  a  funnel,  precautions  being  taken  to  exclude  dust.  The 
deposit  is  washed  from  the  filter  paper  into  the  micro- 
filter  by  means  of  a  jet  of  pure  water.  The  suspended 
matter  collects  on  the  top  of  the  clay  plug  and  is  measured 
by  noting  its  height.  If  the  clay  plug  is  blocked  the  ap- 
plication of  a  filter-pump  may  be  needed.  When  the  column 
of  water  in  the  small  tube  is  only  about  a  centimeter  in 
height,  the  main  body  of  the  tube  is  cut  away  by  means  of 
a  file  scratch  and  the  deposit  loosened  from  the  filter  plug, 
if  necessary,  by  the  use  of  a  platinum  wire.  The  tube  is 
inverted  so  as  to  bring  the  deposit  to  the  open  end,  and 
then  cut  off  close  to  the  plug.  By  this  means  the  sus- 
pended matter  is  collected  in  a  short  capillary  tube  open 
at  both  ends.  By  gentle  ^haking,  the  contents  may  be 
brought  onto  a  glass  slide. 

Owing  to  the  great  differences  in  the  size  of  microscopic 
organisms,  the  mere  enumeration  of  their  numbers  is  not 
always  an  index  of  the  amount  of  living  matter  in  sus- 
pension. To  obviate  this,  Whipple  has  suggested  a  stan- 
dard unit  of  size,  estimating  by  means  of  it  the  total  volume 
of  the  organisms,  and  not  their  number.  He  finds  by 
this  method  that  the  analytic  and  biologic  results  corre- 
spond much  more  closely  than  when  mere  numbers  are 
recorded.  The  unit  is  an  area  of  400  microns — that  is, 
a  square  of  20  microns  on  a  side.  The  results  are  stated 
in  number  of  standard  units  per  cubic  centimeter. 

Mr.  Whipple  has  investigated  the  conditions  influencing 
the  growth  of  the  microscopic  organisms  in  water.  He 
finds  that  diatoms  thrive  best  with  a  supply  of  nitrates  and 


74  ANALYTIC   OPERATIONS. 

a  free  circulation  of  air;  temperature  alone  has  no  very 
direct  effect.  Infusoria  will  be  found  in  largest  numbers 
when  the  water  contains  the  greatest  amount  of  finely 
divided  organic  matter.  When  the  conditions  bring  about 
a  circulation  of  the  water,  the  organisms  are  not  only 
brought  constantly  in  contact  with  new  food  materials, 
but  are  enabled  to  reach  the  upper  layers  of  the  water  where 
oxygen  is  abundant. 

Bacteriologic  examinations  may  be  qualitative  or 
quantitative.  The  former  involves  the  determination  of 
the  species  of  microbes  present,  especially  those  having 
disease-producing  power,  or  characteristic  of  some  form  of 
pollution.  The  processes  are  usually  laborious,  requiring 
extensive  laboratory  facilities.  Quantitative  examination — 
microbe-counting,  as  it  may  be  called — is  the  determination 
of  the  number  of  microbes,  or  microbe-colonies,  that  can 
be  grown  from  a  given  volume  of  water  under  specified 
conditions.  As  the  growth  of  living  organisms  is  influenced 
by  all  external  conditions,  the  results  of  the  culture  of 
microbes  are  not  comparable  with  one  another,  unless 
strict  uniformity  of  methods  has  been  observed.  Neglect 
of  this  fact  renders  a  very  large  part  of  the  earlier  \vork  and 
some  of  the  present-day  work  of  little  statistical  value. 
Among  the  conditions  materially  affecting  the  growth  of 
microbes  are  temperature,  reaction  of  the  culture-medium 
to  different  indicators,  degree  of  exposure  to  light  and  air, 
and  duration  of  cultivation.  The  composition  of  the 
culture-medium  has  much  influence,  and  it  is  difficult  to 
control  this  exactly,  owing  to  the  irregularity  of  quality 
of  some  of  the  materials  used. 

At  the  present  day,  microbe-counting  for  water  analysis 


SANITARY   EXAMINATIONS.  75 

is  done  almost  entirely  with  culture-media  that  are  solid 
at  ordinary  temperatures  but  may  be  liquefied  at  or  near 
blood-heat.  Gelatin  or  agar  is  used  for  producing  the 
solidity.  The  former  is  the  most  convenient,  but  its  jelly 
melts  at  such  a  low  temperature  that  it  is  of  limited  ap- 
plication, and  agar  is  largely  employed. 

Apparatus  for  bacteriologic  work  is  now  all  furnished 
of  good  quality  by  dealers,  and  will  not  need  special  de- 
scription. For  the  ordinary  methods  of  microbe-counting 
the  following  will  be  needed : 

Open-steam  Sterilizer.  A  modification  of  the  Arnold 
sterilizer  is  now  much  used. 

Autoclave,  a  closed-steam  sterilizer,  permitting  the  ap- 
plication of  temperatures  much  above  the  boiling  point  of 
water. 

Hot  Air  Oven  for  special /sterilizations. 

Culture  Oven,  with  thermostat. 

Double  Boiler  of  agate  or  other  good  culinary  ware. 
The  inner  vessel  should  have  a  capacity  of  a  little  more 
than  a  liter. 

Test-tubes,  about  12  cm.  long  and  1.5  cm.  in  diameter. 

Petri  dishes,  about  10  cm.  in  diameter  and  i.o  cm.  deep. 
As  far  as  possible,  dishes  of  uniform  size  should  be  selected. 
Each  dish  and  cover  should  be  marked  in  the  center  by  a 
diamond  with  a  distinguishing  number. 

Wire  baskets  for  holding  several  dozen  test-tubes. 

Fermentation-tube,  such  as  used  in  the  detection  of  sugar 
in  urine. 

Ordinary  laboratory  appliances,  such  as  pipets,  burets, 
funnels,  beakers,  and  cotton-wool.  Tin-foil  cut  in  squares 
5  cm.  on  the  side. 


76  ANALYTIC   OPERATIONS. 

The  materials  for  preparing  culture-media  should  be 
obtained  from  responsible  dealers,  who  will  furnish  the 
grades  regularly  used.  The  following  will  assist  in  the 
selection. 

Gelatin.  A  grade  made  in  Germany  and  distinguished 
by  a  monogram  of  the  initials  WH  is  used. 

A  gar.     A  colorless  grade  is  preferable. 

Peptone.     Witte's  dry  peptone  is  used. 

Glucose.  The  grade  termed  "crystallized  pure"  is 
preferred;  it  consists  principally  of  dextrose. 

Meat-extract.  That  made  by  the  Liebig  Meat-Extract 
Company,  limited,  of  London,  is  almost  the  only  form 
used  by  bacteriologists,  but  there  seems  to  be  no  reason 
for  preference  to  some  of  the  American  extracts. 

Sodium  chlorid.     A  good  quality  of  table  salt  will  suffice. 

Glycerol  should  be  as  free  as  possible  from  acid  and 
mineral  matters. 

Lactose  should  be  of  high  purity,  especially  free  from 
milk-proteids. 
Preparation  of  Culture-media : 

Bouillon  is  the  term  applied  to  many  forms  of  liquid 
media,  prepared  with  meat  juice  or  meat-extract.  The 
ordinary  bouillon  is  prepared  according  to  the  following 
formula : 

Five  hundred  grams  of  finely-chopped  meat,  as  free  as 
possible  from  fat  and  gristle,  are  soaked  overnight  in  about 
a  liter  of  cold  water,  at  a  temperature  between  o°  C.  and 
10°  C.  The  mass  is  then  strained  through  a  coarse  towel  and 
pressed  until  as  much  as  possible  of  the  liquid  is  obtained. 
To  this  is  added  10  grams  of  peptone  and  5  grams  of  com- 
mon salt.  It  is  then  heated  to  boiling,  best  in  the  open- 


SANITARY   EXAMINATIONS.  77 

steam  sterilizer,  to  coagulate  albumin,  after  which  it  is 
filtered.  The  most  difficult  point  in  the  work  is  neu- 
tralization. This  is  often  accomplished  by  the  use  of 
sodium  carbonate,  which  is  added  in  small  amounts  until 
the  liquid  no  longer  affects  red  litmus  paper.  The  better 
method  is  to  titrate  a  portion  of  the  bouillon  with  sodium 
hydro xid  solution,  and  calculate  from  this  the  amount 
of  that  solution  necessary  to  neutralize  the  whole  of  the 
liquid.  Fuller  has  devised  a  good  method  of  procedure. 
The  bouillon  is  made  up  when  cool  to  a  definite  volume, 
say  1000  c.c.;  5  c.c.  are  mixed  with  45  c.c.  of  distilled  water 
in  a  porcelain  dish,  boiled  for  three  minutes,  i  c.c.  of  solu- 
tion of  phenolphthalein  added,  and  quickly  titrated  with 
twentieth  normal  sodium  hydroxid.  The  neutral  point 
is  the  slight  pink  color  not  disappearing  on  gentle  stirring. 
From  the  number  of  cubic,  centimeters  used  the  amount 
of  alkali  needed  to  neutralize  the  whole  solution  is  cal- 
culated, but  this  alkali  should  be  added  in  the  form  of 
normal  solution  in  order  to  avoid  much  dilution  of  the 
bouillon. 

Bouillon  may  be  modified  in  many  ways,  by  the  ad- 
dition of  different  substances,  but  the  inherent  or  possible 
acidity  or  alkalinity  of  these  must  be  ascertained  and 
corrected  if  culture  results  are  to  be  kept  standard. 

A  dextrose  bouillon  for  special  fermentation  work  is 
made  by  adding  glucose  in  the  proportion  of  20  grams 
to  1000  c.c.  of  the  liquid. 

Meat-extract  is  often  used  instead  of  the  infusion  of 
chopped  meat.  Five  grams  of  a  good  commercial  extract 
are  used  for  each  1000  c.c.  of  bouillon. 

Gelatin  Media. — The  ingredients,  other  than  the  gelatin, 


78  ANALYTIC   OPERATIONS. 

are  dissolved  and  treated  as  described  in  the  making 
of  bouillon.  After  neutralization,  the  gelatin  is  dissolved 
by  gentle  heating.  If  this  contributes  any  acidity,  it  must 
be  neutralized.  The  heating  may  be  done  in  the  double 
boiler.  The  liquid  should  not  be  heated  strongly  or  for  a 
long  time,  as  the  gelatinizing  property  may  be  injured. 
The  solution  is  made  up  to  the  proper  volume  and  filtered 
through  paper. 

Meat-extract  peptone- gelatin. 

Meat-extract, - 5.0  grams 

Peptone, 10.0      " 

Gelatin,    150.0      " 

Dextrose,   2.0      " 

Sodium  chlorid, 5.0       " 

Water, 1000.0  c.c. 

The  preparation  of  agar  solution  is  more  difficult  than 
that  of  gelatin.  Several  methods  have  been  suggested. 
Ravenel  uses  high  pressure,  according  to  the  following 
methods : 

Preferable  Method: 

(A)  Chopped  meat, 500  grams 

Water, 500  c.c. 

These  are  mixed  and  allowed  to  stand  overnight. 

(B)  Agar,   12  grams 

Water, 500  c.c. 

Solution  B  is  put  into  the  autoclave,  the  pressure  run  up 
to  2  atmospheres,  the  heat  withdrawn,  and  the  boiler 
opened  when  the  temperature  has  fallen  a  little  below 
100°  C.  The  solution  is  allowed  to  cool  to  about  75°  C. 
(below  the  coagulating  point  of  albumin),  10  grams  of 


SANITARY   EXAMINATIONS.  79 

dried  peptone  and  5  grams  of  sodium  chlorid  are  added, 
A  and  B  mixed,  the  liquid  boiled  for  about  three  minutes, 
neutralized  and  filtered.  The  filtration  is  very  quick — 
from  ten  to  twelve  minutes  for  a  liter.  A  hot-water  funnel 
is  not  needed,  but  the  filter  must  be  moistened  with  boiling 
water  immediately  before  pouring  in  the  agar.  In  the  pro- 
cess with  fresh  meat  the  clarification  is  effected  by  the 
coagulation  of  the  albumin  in  the  meat-water,  hence  solu- 
tion B  must  not  be  added  to  A  until  cool  enough  to  avoid 
coagulation. 
Alternative  method: 

(A)  Dried  peptone,   10  grams 

Common  salt, 5      " 

Meat-extract,    5      " 

Water, 500  c.c. 

Boil  for  three  minutes  and  neutralize. 

(B)  Agar-agar, 12  grams 

Water, 500  c.c. 

The  agar  is  chopped  fine  and  heated  in  the  autoclave 
to  two  atmospheres.  As  soon  as  this  pressure  is  reached, 
the  heat  is  withdrawn  and  the  liquid  allowed  to  cool  until 
below  100°  C.  before  opening.  The  two  solutions  A  and 
B  are  then  mixed,  cooled  to  60°  C.,  the  whites  of  two  eggs 
beaten  in  50  c.c.  of  water  added,  well  stirred  in,  and  the 
whole  then  boiled  and  filtered  through  paper. 

Instead  of  the  white  of  egg,  blood-serum  may  be  used, 
which  seems  to  add  also  to  the  nutritive  value  of  the  medium. 
Agar  made  with  meat-extract  will  often  form  a  precipitate 
during  the  sterilization. 

Abbott  gives  the  following  method  of  preparing  agar 
solution:  The  bouillon  is  prepared  and  neutralized  in 


8o  ANALYTIC   OPERATIONS. 

the  usual  way,  then  15  grams  of  finely  chopped  agar  are 
added,  and  water  sufficient  to  make  the  volume  1250  c.c. 
The  mass  is  boiled  gently  over  a  direct  flame,  stirring 
occasionally,  for  several  hours.  If  the  fluid  goes  below  the 
liter  level,  enough  water  should  be  added  to  make  up  the 
amount.  The  boiling  should  be  continued  until  about 
a  liter  is  left  in  the  vessel.  When  the  solution  of  the  agar 
is  attained,  the  vessel  is  placed  in  a  large  dish  of  cold  water, 
until  it  has  cooled  to  about  70°  C.,  the  white  of  one  egg 
that  has  been  beaten  up  with  water  added,  mixed  well, 
and  boiled  again  for  a  half-hour,  avoiding  the  evaporation 
of  the  liquid  below  the  liter  point.  The  liquid  is  filtered 
through  heavy  folded  filter  paper  at  room-temperature. 
It  is  necessary  that  the  solution  should  be  not  above  70°  C. 
when  the  white  of  egg  is  added  or  it  will  become  lumpy. 
Commercial  egg-albumin  in  10  per  cent,  solution  in  water 
may  be  used  instead  of  white  of  egg.  The  solution  thus 
prepared  should  filter  rapidly. 

Potato  Culture. — Cultivation  on  potatoes  has  been  much 
used  as  a  method  of  distinguishing  certain  microbes. 
Large,  sound  potatoes  should  be  selected,  thoroughly 
washed,  and  cut  into  disks  about  five  centimeters  in  diam- 
eter and  one  centimeter  thick.  These  are  placed  in  glass 
boxes  (pomade  boxes)  which  have  lids  with  ground  joint, 
and  heated  for  about  one-half  hour  in  the  sterilizer.  An- 
other method  is  to  cut  out  cylinders  with  the  aid  of  an 
apple-corer,  or  largest  size  cork-borer,  slice  these  obliquely, 
and  place  them  in  test-tubes,  which  are  then  closed  with 
cotton  plugs  and  sterilized.  The  latter  method  does  not 
give  a  large  surface,  but  the  growth  of  any  inoculation 
may  be  easily  watched. 


SANITARY  EXAMINATIONS.  8 1 

Many  special  forms  of  culture-media  are  employed  for 
bacteriologic  investigations  which  do  not  come  within  the 
line  of  water  analysis,  and  need  not  be  described.  One 
form  is  much  employed  in  the  search  for  the  specific  germ 
of  typhoid  fever,  namely,  Wiirtz's  litmus -lactose  solution. 
This  may  be  with  either  agar  or  gelatin,  in  conjunction 
with  meat  extract.  The  nutrient  medium  must  be  made 
so  as  to  possess  such  a  degree  of  alkalinity  that  10  c.c. 
will  neutralize  0.5  c.c.  of  decinormal  sulfuric  acid.  Lactose 
is  added  in  the  proportion  of  two  or  three  grams  to  100  c.c. 
of  medium  and  the  mixture  sterilized,  after  which  sufficient 
sterilized  litmus  tincture  is  added  to  give  the  fluid  a  dis- 
tinct but  not  deep-blue  color. 

Cultivation  in  gelatin  at  ordinary  temperatures  usually 
yields  a  larger  number  of  points  of  microbic  life  than  in 
agar  at  blood-heat.  This  js  due  to  the  fact  that  many 
common  water-bacteria  do  not  grow  well  at  the  higher 
temperatures. 

Culture-media  when  ready  for  use  are  distributed  in 
test-tubes.  These  must  be  well  cleaned.  In  laboratories 
in  which  regular  chemical  work  is  done  the  solution  of 
crude  chromic  and  sulfuric  acids  used  for  voltaic  batteries 
is  a  good  cleaning  agent,  the  tubes  being  soaked  in  this 
for  about  a  day,  and  then  rinsed  thoroughly  and  sterilized 
as  noted  below.  In  bacteriologic  laboratories  it  is  usual 
to  cleanse  the  tubes  with  a  3  per  cent,  solution  of  sodium 
hydro xid.  The  tubes  are  boiled  in  the  solution,  rinsed, 
swabbed  out  with  a  brush,  and  allowed  to  dry  in  the  inverted 
position.  A  cotton-wool  plug  is  made  for  each  tube,  care 
being  taken  that  it  fits  neatly,  without  creases  or  channels 
and  not  too  tightly.  The  projecting  part  of  the  plug  is 


82  ANALYTIC   OPERATIONS. 

clipped  moderately  close  and  a  tinfoil  cap  placed  on  each. 
The  arrangement  is  sterilized  in  the  hot-air  oven' at  150°  C. 
When  cold,  the  tinfoil  and  plug  are  carefully  removed, 
about  10  c.c.  of  culture-medium  put  into  each  tube,  with 
as  little  outside  contamination  as  possible,  the  plug  and 
cap  replaced,  and  the  tubes  and  contents  sterilized  in  the 
open-steam  sterilizer.  The  wire  baskets  are  used  to  hold 
the  tubes  during  the  sterilizations. 

For  making  cultures  definite  volumes  of  the  water  sample 
are  introduced  into  the  culture-medium,  and  if  this  is  a 
solidifying  form,  it  is  put  into  the  Petri  dish.  All  the 
manipulations  must  be  conducted  with  great  care  to  avoid 
contamination.  When  there  is  no  clue  to  the  amount 
of  microbes  present,  it  will  be  necessary  to  make  cultures 
with  different  proportions  of  water.  Some  tubes  may  be 
inoculated  with  a  few  drops,  some  with  three  to  five  drops, 
and  some  with  i  c.c.  Some  operators  dilute  the  water 
considerably  and  take  small  measured  volumes.  If  this 
method  is  used,  the  diluting  water  must  be  distilled  and 
have  been  well  sterilized,  by  at  least  five  minutes'  boiling, 
and  cooled  out  of  contact  of  air.  All  pipets,  dishes,  and 
other  apparatus  that  come  in  contact  with  the  water  must 
have  been  first  sterilized. 

The  test-tubes  containing  the  culture-medium  are 
warmed  gently,  just  enough  to  render  the  culture-medium 
fluid,  the  desired  volume  of  the  water  added,  the  mixture 
shaken  and  promptly  poured  into  the  Petri  dishes,  covered 
and  placed  in  the  oven,  which  should  have  been  already 
raised  to  the  temperature  at  which  it  is  desired  to  conduct 
the  work.  Unless  specially  desired  otherwise,  cultures 
should  be  made  in  the  dark.  They  may  be  made  at  any 


SANITARY   EXAMINATIONS.  83 

temperature  short  of  that  at  which  the  medium  melts,  but 
either  ordinary  temperature  or  37°  C.  is  usually  selected. 
The  condition  of  the  plates  should  be  observed  at  intervals 
of  twenty-four  hours,  and  the  points  of  microbic  life 
counted  and  recorded.  After  some  days  the  growth  will 
become  so  luxuriant  or  the  liquefaction  of  the  medium  so 
extensive  that  accurate  observation  is  not  possible. 

If  the  microbic  points  are  numerous,  it  will  be  necessary 
to  employ  a  counting  scale.  For  the  Petri  dish,  Pake's 
modification  of  Lafar's  scale  is  cheap  and  sufficient. 

General  Character  of  the  Microbes  in  Natural 
Waters. — The  microorganisms  of  natural  waters  are  prin- 
cipally included  in  the  genera  Bacillus  and  Spirillum, 
especially  the  former.  Micrococci  and  molds  are  rare, 
and  are  generally  due  to  contamination  by  dust. 

Microbes  are  distinguished  according  to  the  conditions 
favorable  to  their  growth,  as  follows: 

Saprophytic.     Growing  on  dead  matter. 

Parasitic.     Growing  only  on  living  matter. 

Aerobic.     Requiring  free  oxygen. 

Anaerobic.     Not  requiring  free  oxygen. 

When  the  organism  possesses  the  power  of  adapting 
itself  to  different  conditions,  the  term  facultative  is  applied; 
when  it  can  grow  only  under  special  conditions,  the  term 
obligatory  is  applied. 

Microbes  are  also  differentiated  by  the  effect  which  they 
produce  upon  the  culture-medium.  Some  species  rapidly 
or  slowly  liquefy  the  jelly  with  evolution  of  foul-smelling 
gases;  others — chromogenic  microbes — produce  character- 
istic colors.  Many  do  not  produce  any  positive  modifica- 
tion, and  for  purposes  of  distinction  it  is  usual  to  transfer 


84  ANALYTIC   OPERATIONS. 

portions  of  the  colonies  to  other  culture-media.  Such 
special  cultures  are  obtained  by  taking  up  a  portion  of 
the  colony  on  the  end  of  a  wire  which  has  been  just  ster- 
ilized by  heating  to  redness  and  inoculating  the  prepared 
medium. 

Indol  Reaction. — Indol,  C8H7N,  more  properly  indin, 
is  a  weak  base,  which  is  a  product  of  the  growth  of  many 
species  of  microbes,  and  the  detection  of  it  may,  therefore, 
be  utilized  as  a  differentiation  test.  Kitasato  gives  the 
following  method  for  performing  the  test: 

Ten  c.c.  of  an  alkaline-peptone-meat  infusion  (without 
gelatin),  which  has  been  previously  inoculated  with  the 
microbes  to  be  tested,  and  kept  for  twenty-four  hours  at 
blood-heat,  are  treated  with  i  c.c.  of  solution  of  pure 
potassium  nitrite  (0.02  gram  in  100  c.c.)  and  then  with 
a  few  drops  of  concentrated  sulfuric  acid.  In  the  presence 
of  indol  a  rose  or  deep-red  color  is  developed.  Spirillum 
cJwlercB  and  Bacillus  coli  communis  give  the  reaction  strongly; 
S.  Finkleri  feebly;  the  so-called  B.  typhosus  ordinarily 
does  not  give  it. 

Careful  and  experienced  bacteriologists  do  not  now  claim 
to  be  able  to  isolate  the  typhoid  bacillus  from  natural 
waters.  The  effort  has  failed  even  with  waters  that  are 
obviously  polluted.  In  default  of  a  method  for  such  de- 
tection, resort  is  had  to  methods  for  the  detection  of  the 
microbe  known  as  Bacillus  coli  communis.  This  being 
a  constant  inhabitant  of  the  intestinal  canal  of  the  highest 
animals,  and  being  almost  always  associated  with  dangerous 
pollution,  the  detection  of  it  in  water  indicates  previous 
contamination.  This  organism  is  not  constant  in  character, 
but,  in  common  with  many  other  dangerous  microbes, 


SANITARY    EXAMINATIONS.  85 

grows  well  at  blood-heat,  while  many  common  water,  air, 
and  soil  organisms  do  not.  Some  mild  germicides  also 
affect  the  latter  class  of  microbes  more  than  the  intestinal 
bacilli.  Upon  these  principles  have  been  founded  many 
methods  for  differentiation,  two  of  which  are  in  common  use. 

The  Franklands,  after  reviewing  at  length  the  various 
methods  that  have  been  suggested  for  differentiating  the 
typhoid  bacillus,  show  that  most  of  them  are  quite  insuffi- 
cient. A  routine  treatment  is,  however,  suggested  as  fol- 
lows: 

The  water  is  freed  from  the  ordinary  water-bacteria 
by  preliminary  culture  in  Parietti's  solution.  This  is  a 
phenol-broth  prepared  by  mixing  10  c.c.  of  neutral  bouillon 
with  0.25  c.c.  of  the  following  solution: 

Phenol,    5  grams 

Hydrochloric  acid, '_ 4      " 

Water, 100      " 

This  solution  is  sterilized  by  heating  it  for  twenty-four 
hours  at  37°  C.  The  tubes  are  then  inoculated  with  from 
one  to  ten  drops  of  the  water  sample,  which  must  be  thor- 
oughly mixed  with  the  broth,  and  again  kept  in  the  sterilizer 
for  not  less  than  forty-eight  hours.  If  any  of  the  tubes 
appear  turbid  after  the  treatment  they  should  be  submitted 
to  plate  cultivation,  and  any  colonies  which  resemble  those 
produced  by  the  typhoid  bacillus  should  be  further  studied 
by  inoculation  into  gelatin  tubes  to  observe  the  gas-pro- 
ducing test,  into  milk  to  note  if  coagulation  occurs,  and 
by  cultivation  in  broth  to  determine  if  indol-reaction  will 
be  obtained. 

The  method  of  Theobald  Smith  is  to  cultivate  the  water 


86  ANALYTIC   OPERATIONS. 

sample  at  blood-heat  with  a  bouillon  rich  in  dextrose  and 
note  whether  there  is  evolution  of  gas.  The  fermentation 
tube  is  used.  Sufficient  bouillon  is  put  in  to  fill  the  upright 
stem  and  the  curved  part,  but  not  much  of  the  bulb.  The 
whole  is  then  well  sterilized  in  the  open  steam  sterilizer,  a 
cotton  plug  with  tinfoil  cover  having  been  previously  placed 
in  the  opening  of  the  bulb.  The  apparatus  is  cooled ;  a  few 
drops  of  the  water  sample  are  then  introduced  into  the 
bouillon,  taking  care  not  to  allow  outside  contamination, 
the  plug  and  tinfoil  are  replaced,  and  the  tube  kept  at  37°  C. 
for  about  forty  hours.  An  accumulation  of  gas  at  the  top 
of  the  tube  indicates  that  microbes  of  the  type  of  the  B. 
coli  communis  are  present.  Several  tubes  and  one  or  two 
control  tubes,  that  is,  tubes  which  are  not  inoculated  with 
water,  should  be  tried  together.  Portions  of  the  gas-pro- 
ducing bouillon  may  be  inoculated  into  sterile  agar  and 
cultivated  at  the  same  temperature  after  pouring  into  the 
Petri  dish. 

The  bouillon  is  made  according  to  the  procedure  on 
page  76,  except  that  20  grams  of  glucose  are  used  to  the 
liter. 

The  resemblance  between  the  two  forms,  B.  typhosits 
and  B.  coli  communis,  is  so  great,  and  the  variability  of 
both  forms  so  marked,  that  some  observers  have  suggested 
that  they  are  but  varieties  of  the  same  specific  bacillus. 
Much  attention  has  been  paid  to  the  distinctions.  The 
following  synopsis  has  been  given  by  Abbott: 


TECHNIC   EXAMINATIONS.  87 

CHARACTERISTICS.  B.  TYPHOSUS.  B.  COLI  COMMUNIS. 

Motility, Conspicuous.  Not  marked. 

Growth  in  gelatin,   ___Slow.  Not  very  slow. 

"       "  potato, Usually  inconspicu-      Always  rapid  and  visi- 

ous.  ble. 

"        "  milk, No    coagulation;     no  Acidity    and    coagula- 

acidity.  tions    in    forty-eight 

hours  in  incubator  at 
38°  C. 

Growth  in  media  con- 
taining glucose,  lac- 
tose, or  sucrose, No  evolution  of  gas.  Marked  evolution  of 

gas. 

Growth  in  media  con- 
taining lactose  and 

litmus,   Colonies  pale  blue;  no  Colonies     pink;       sur- 

reddening    of    sur-      rounding       medium 
rounding  medium.        red. 
Indol  reaction  in  pep-  / 

tone  solution  (forty- 
eight  hours  at  38°  C.) Rarely  present.  Always  present. 

It  will  be  seen  that  the  characteristics  of  B.  typhosus  are 
rather  negative  than  positive.  The  data  are  derived  from 
cultures  obtained  from  intestinal  discharges  or  viscera  of 
patients  affected  with  typical  typhoid  fever. 


TECHNIC    EXAMINATIONS. 
GENERAL  QUANTITATIVE  ANALYSIS. 

Silica,  Iron,  Aluminum,  Manganese,  Calcium,  and 
Magnesium. — One  liter  of  the  water  acidified  with  hy- 
drochloric acid  is  evaporated  to  complete  dryness,  best 
in  a  platinum  dish,  the  residue  treated  with  hydrochloric 


ANALYTIC   OPERATIONS. 

acid  and  water,  and  the  separated  silica  filtered,  washed, 
dried,  ignited  in  a  platinum  crucible,  and  weighed. 

To  the  filtrate,  previously  boiled  with  a  few  drops  of 
strong  nitric  acid,  slight  excess  of  ammonium  hydroxid  is 
added,  the  liquid  boiled  several  minutes,  the  precipitate 
collected,  washed  thoroughly  with  boiling  water,  dried, 
ignited,  and  weighed.  It  consists  of  Fe2O3  and  A12O3. 
It  also  contains  all  the  phosphates  and  some  manganese  if 
much  is  present  in  the  water.  In  such  cases  the  precipitate 
before  drying  is  redissolved  in  hydrochloric  acid  and 
neutralized  with  a  dilute  solution  of  ammonium  carbonate 
until  the  water  becomes  almost  turbid.  It  is  then  boiled, 
and  the  precipitate,  now  free  from  manganese,  washed, 
dried,  ignited,  and  weighed.  The  iron  may  be  determined 
by  dissolving  the  precipitate  in  strong  hydrochloric  acid 
and  employing  the  colorimetric  method  described  on  page 
66. 

If  no  manganese  or  only  traces  are  present,  the  filtrate 
from  the  iron  is  mixed  with  sufficient  ammonium  chlorid 
to  prevent  the  precipitation  of  the  magnesium,  ammonium 
hydroxid,  and  then  ammonium  oxalate  added  in  quantity 
sufficient  to  precipitate  the  calcium  and  to  convert  all  the 
magnesium  into  oxalate,  and  thus  hold  it  in  solution.  The 
precipitate  contains  all  the  calcium  and  some  of  the  magne- 
sium. If  the  magnesium  is  present  only  in  relatively  small 
quantity,  the  amount  carried  down  may  be  disregarded; 
otherwise  a  second  precipitation  should  be  made  as  follows: 
The  solution  is  allowed  to  stand  until  the  precipitate  has 
subsided;  this  will  require  some  hours.  The  supernatant 
liquid  is  poured  off  through  a  filter,  the  precipitate  washed 
by  decantation,  then  dissolved  in  hydrochloric  acid,  water 


TECHNIC   EXAMINATIONS.  89 

added,  then  ammonium  hydroxid  and  a  small  quantity 
of  ammonium  oxalate.  After  the  calcium  oxalate  has 
thoroughly  subsided  it  is  filtered  off,  washed,  and  dried.  If 
quite  small  in  amount,  it  is  placed  with  the  filter  in  a  weighed 
platinum  crucible,  ignited  over  the  Bunsen  burner  for  a 
short  time,  and  then  over  the  blast  lamp  for  from  five  to 
fifteen  minutes.  The  calcium  is  thus  obtained  in  the  form 
of  oxid,  which  is  allowed  to  cool  in  the  desiccator  and 
weighed.  The  weight  thus  obtained  multiplied  by  0.714 
gives  the  weight  of  calcium.  When  the  amount  of  precipi- 
tate is  large,  it  is  better  to  remove  it  from  the  filter,  and 
heat  it  just  short  of  redness  until  it  assumes  a  grayish  tint. 
It  then  consists  of  calcium  carbonate.  To  this  is  added 
the  ash  of  the  filter.  The  weight  of  the  calcium  carbonate 
multiplied  by  0.4  gives  the  weight  of  calcium. 

The  calcium  may  be/  determined  by  titration.  The 
precipitate  of  calcium  oxalate,  after  thorough  washing,  is 
dissolved  from  the  filter  by  warm,  dilute,  sulfuric  acid, 
heated  to  about  65°  C.,  and  titrated  with  decinormal  per- 
manganate until  a  pink  tint  is  obtained.  One  c.c.  of  the 
permanganate  is  equivalent  to  0.0020  calcium;  0.0028  cal- 
cium oxid;  0.0050  calcium  carbonate. 

The  filtrates  are  mixed,  slightly  acidified  with  hydro- 
chloric acid,  concentrated  and  cooled,  ammonium  hydroxid 
and  sodium  phosphate  added  in  excess,  stirred  briskly 
and  allowed  to  stand  in  the  cold  for  about  twelve  hours. 
The  precipitated  ammonium  magnesium  phosphate  is 
brought  upon  a  filter,  that  adhering  to  the  sides  of  the  vessel 
being  dislodged  by  rubbing  with  a  glass  rod  tipped  with 
a  piece  of  clean  rubber  tubing.  It  is  washed  with  a  solu- 
tion made  by  mixing  one  part  of  the  ammonium  hydroxid 


90  ANALYTIC   OPERATIONS. 

of  0.96  sp.  gr.  with  three  parts  of  water.  The  precipitate 
is  dried,  transferred  to  a  platinum  crucible,  the  filter  ashed 
separately  and  added  to  it,  and  the  whole  heated  at  first 
gently  and  then  to  intense  redness  for  several  minutes. 
After  cooling,  it  is  weighed.  It  consists  of  magnesium 
pyrophosphate ;  the  weight  multiplied  by  0.218  gives  the 
weight  of  magnesium. 

Manganese,  if  present  in  appreciable  quantity,  is  sepa- 
rated before  the  precipitation  of  the  calcium,  as  follows: 
The  filtrate  from  the  iron  precipitate  is  slightly  acidulated 
with  hydrochloric  acid,  concentrated,  and  the  manganese 
precipitated  as  sulfid  by  colorless  or  slightly  yellow  solu- 
tion of  ammonium  sulfid.  The  flask,  which  should  be 
nearly  full,  is  stoppered,  allowed  to  rest  in  a  moderately 
warm  place  until  the  precipitate  has  thoroughly  settled, 
filtered,  washed  with  dilute  ammonium  sulfid  water,  and 
purified  by  dissolving  in  a  small  quantity  of  hydrochloric 
acid  and  reprecipitating  with  ammonium  sulfid.  It  is 
filtered  off,  washed  as  before,  dried,  placed  in  a  weighed 
porcelain  crucible,  covered  with  a  little  sulfur,  and  ignited 
in  a  current  of  hydrogen  introduced  into  the  crucible  by  a 
tube  passing  through  a  hole  in  the  cover.  The  pure  man- 
ganese sulfid  thus  obtained  is  allowed  to  cool  and  weighed. 
The  weight  multiplied  by  0.633  giyes  manganese. 

Sulfates. — Five  hundred  c.c.  of  the  clear  water  are 
slightly  acidulated  with  hydrochloric  acid,  heated  to  boil- 
ing, and  barium  chlorid  solution  added  in  moderate  ex- 
cess. The  precipitated  barium  sulfate  is  allowed  to  sub- 
side completely,  collected  upon  a  filter,  washed  thoroughly, 
dried,  and  incinerated.  The  weight  multiplied  by  0.411 
gives  SO4.  If  the  proportion  is  very  low,  it  will  be  ad  vis- 


TECHNIC   EXAMINATIONS.  9 1 

able  to  concentrate  the  water  to  one-fifth  or  one-tenth  its 
bulk  before  precipitating. 

Control.  Potassium,  Sodium,  and  Lithium. — From 
250  to  1000  c.c.  of  the  water,  according  to  the  amount  of 
solid  matters  present,  are  evaporated  to  dryness  in  a  plati- 
num dish,  and  the  residue  treated  with  a  small  amount  of 
water  and  sufficient  dilute  sulfuric  acid  to  decompose  the 
salts  present.  The  dish  should  then  be  covered  and  placed 
upon  the  water-bath  for  five  or  ten  minutes,  after  which 
any  liquid  spurted  on  the  cover  is  washed  into  the  dish,  the 
whole  evaporated  to  dryness  and  heated  to  redness.  A 
few  drops  of  ammonium  carbonate  solution  should  then  be 
mixed  with  the  residue,  and  the  ignition  repeated  to  insure  the 
removal  of  the  last  portions  of  free  acid.  In  the  majority 
of  cases  the  only  basic  elements  present  in  considerable 
quantity  are  calcium,  magnesium,  and  sodium.  The 
sodium  may  be  determined  indirectly,  therefore,  by  cal- 
culating from  the  amount  of  calcium  and  magnesium 
found,  the  calcium  and  magnesium  sulfate  in  the  residue, 
and  subtracting  this  sum,  together  with  the  silica,  from  the 
total  residue. 

For  the  determination  of  potassium  and  sodium  in  ordi- 
nary well  and  river  waters,  not  less  than  two  liters  should 
be  employed.  When  lithium  is  to  be  determined,  it  is 
generally  necessary  to  use  much  more.  In  any  case,  as 
the  alkalies  are  to  be  weighed  as  chlorids,  it  is  advisable, 
if  notable  amounts  of  sulfates  are  present,  to  precipitate 
them  by  addition  of  barium  chlorid. 

The  water  is  evaporated  to  about  200  c.c.,  a  slight  excess 
of  calcium  hydroxid  added  to  the  hot  liquid, — generally 
three  c.c.  of  thin  milk  of  lime  will  be  sufficient, — and  the 


92  ANALYTIC   OPERATIONS. 

heat  continued  for  several  minutes.  It  is  then  washed 
into  a  250  c.c.  flask,  disregarding  the  insoluble  portion  ad- 
hering to  the  dish,  which,  however,  should  be  thoroughly 
washed,  and  the  washings  added  to  the  flask.  After  cool- 
ing, the  flask  is  filled  up  to  the  mark  with  distilled  water, 
thoroughly  mixed,  the  precipitate  allowed  to  settle,  and 
the  liquid  filtered  through  a  dry  filter.  Two  hundred  c.c. 
of  the  filtrate  are  measured  into  another  250  c.c.  flask, 
ammonium  carbonate  and  ammonium  oxalate  added,  filled 
with  water  up  to  the  mark,  mixed,  allowed  to  settle,  filtered 
through  a  dry  filter,  200  c.c.  of  the  filtrate  measured  off, 
and  evaporated  to  thorough  dryness  in  a  platinum  crucible, 
heating  very  cautiously  at  the  last  stages,  to  avoid  loss 
by  spurting.  The  lowr-temperature  burner  is  suited  for 
this  purpose.  The  crucible  is  now  covered  and  cautiously 
heated  to  dull  redness,  cooled,  and  weighed.  The  residue 
contains  the  potassium,  lithium,  and  sodium  as  chlorids. 
It  contains,  sometimes,  also,  traces  of  magnesium,  which 
may  be  removed  by  treating  again  with  lime  and  ammonium 
carbonate  and  oxalate.  It  is  frequently  of  advantage,  in 
evaporating  these  saline  solutions,  to  add,  when  the  solu- 
tion becomes  concentrated,  several  cubic  centimeters  of 
strong  hydrochloric  acid.  This  precipitates  the  greater 
portion  of  the  salts  in  a  finely  granular  condition,  and 
renders  loss  by  spurting  less  liable  to  occur. 

If  potassium  and  sodium  chlorids  only  are  present,  the 
residue  is  dissolved  in  a  small  quantity  of  water,  an  excess 
of  a  concentrated  neutral  solution  of  platinum  chlorid 
added,  evaporated  to  small  bulk  at  a  low  heat  on  the  water- 
bath,  some  eighty  per  cent,  alcohol  added,  allowed  to 
stand,  the  clear  liquid  decanted  off  on  a  small  filter,  and 


TECHNIC   EXAMINATIONS.  93 

the  residue  washed  in  this  way  several  times  by  fresh,  small 
portions  of  eighty  per  cent,  alcohol.  The  precipitate  is 
then  washed  on  to  the  filter  with  alcohol,  washed  again 
with  eighty  per  cent,  alcohol,  thoroughly  drie'd  and  trans- 
ferred as  far  as  possible  to  a  watch-glass.  The  small  por- 
tion on  the  filter  is  dissolved  off  and  the  solution  placed  in 
a  weighed  platinum  dish  and  evaporated  to  dryness.  The 
main  portion  on  the  watch-glass  is  then  added,  and  the 
whole  dried  to  a  constant  weight  at  about  260°  F.,  cooled, 
and  weighed.  The  weight  thus  found  multiplied  by  0.3 
gives  the  weight  of  potassium  chlorid.  This  subtracted 
from  the  combined  weight  of  the  chlorids  gives  the  weight 
of  sodium  chlorid. 

Lithium,  if  present,  is  best  separated  before  the  treatment 
with  platinum  chlorid.  The  following  method,  devised 
by  Gooch,  gives  good  results:  To  the  concentrated  solution 
of  the  weighed  chlorids,  amyl  alcohol  is  added  and  heat 
applied,  gently  at  first,  to  avoid  bumping,  until  the  water 
disappears  from  the  solution  and  the  point  of  ebullition 
becomes  constant  at  a  temperature  which  is  approximately 
that  at  which  the  alcohol  boils  (270°  F.),  the  potassium 
and  sodium  chlorids  are  deposited,  and  the  lithium  chlorid 
is  dehydrated  and  taken  into  solution.  The  liquid  is  then 
cooled,  and  a  drop  or  two  of  strong  hydrochloric  acid  added 
to  reconvert  traces  of  lithium  hydroxid  in  the  deposit  and 
the  boiling  continued  until  the  alcohol  is  again  free  from 
water.  If  the  amount  of  lithium  chlorid  be  small,  it  will  be 
found  in  the  solution  and  the  potassium  chlorid  and  sodium 
chlorid  in  the  residue,  excepting  traces  which  can  be  allowed 
for.  If  the  lithium  chlorid  exceed  ten  or  twenty  milligrams, 
the  liquid  may  be  decanted,  the  residue  washed  with  amyl 


94  ANALYTIC   OPERATIONS. 

alcohol,  dissolved  in  a  few  drops  of  water,  and  treated  as 
before.  For  washing,  amyl  alcohol,  previously  dehydrated 
by  boiling,  is  to  be  used  and  the  filtrates  are  to  be  measured 
apart  from  the  washings.  In  filtering,  the  Gooch  filter 
with  asbestos  felt  may  be  used  with  advantage,  applying 
gentle  pressure  by  the  aid  of  the  filter-pump.  The  crucible 
and  residue  are  ready  for  weighing  after  gentle  heating 
over  the  low-temperature  burner.  The  weight  of  the  in- 
soluble chlorids  is  to  be  corrected  by  adding  0.00041  for 
every  10  c.c.  of  amyl  alcohol  in  the  filtrate,  exclusive  of  the 
washings,  if  only  sodium  chlorid  be  present;  0.00051  for 
every  10  c.c.  if  only  potassium  chlorid,  and  0.00092  in  the 
presence  of  both  these  chlorids. 

The  filtrate  and  washings  are  evaporated  to  dryness  in  a 
platinum  crucible  heated  with  sulfuric  acid,  the  excess 
driven  off,  and  the  residue  ignited  to  fusion,  cooled,  and 
weighed.  From  the  weight  is  to  be  subtracted,  for  each 
10  c.c.  of  filtrate,  0.0005,  0.00059,  or  0.00109,  according 
as  only  sodium  chlorid,  potassium  chlorid,  or  both  were 
present  in  the  original  mixture. 

Hydrogen    Sulfid. — The    following    method    is    taken 
from  Button's  "Volumetric  Analysis": 
Reagents  Required : 

Centinormal  lodin. — Dry,  commercial  iodin  is  intimately 
mixed  with  one-fourth  its  weight  of  pure  potassium  iodid 
and  gently  heated  between  two  clock-glasses  by  resting 
the  lower  on  a  hot  plate.  The  iodin  sublimes  in  a  per- 
fectly pure  condition.  It  is  allowed  to  cool  under  the 
desiccator,  1.269  grams  weighed  out,  together  with  1.8 
grams  of  pure  potassium  iodid,  dissolved  in  about  50  c.c. 
of  water,  and  the  solution  made  up  exactly  to  a  liter.  The 


TECHNIC   EXAMINATIONS.  95 

liquid  must  not  be  heated,  and  care  should  be  taken  that 
no  iodin  vapor  is  lost.  One  c.c.  is  equivalent  to  0.00017 
H2S.  The  solution  is  best  prepared  in  stoppered  bottles, 
which  should  be  completely  filled  and  kept* in  the  dark. 
It  will  not  even  then  keep  very  long,  and  should  be  stan- 
dardized by  titration  with  a  weighed  amount  of  pure  sodium 
thiosulfate,  which  should  be  powdered  previous  to  weighing, 
and  pressed  between  filter-paper  to  absorb  any  moisture. 
Fifty  c.c.  of  the  iodin  solution,  when  of  full  strength,  will 
require  o.  1 24  gram  of  sodium  thiosulfate. 

Starch  Indicator, — See  page  57. 
Analytic  Process : 

Ten  c.c.,  or  any  other  necessary  volume  of  the  iodin 
solution,  is  measured  into  a  500  c.c.  flask,  and  the  water 
to  be  examined  added  until  the  color  disappears.  Five 
c.c.  of  starch  liquor  are  then  added,  and  the  iodin  solution 
run  in  until  the  blue  copper  appears;  the  flask  is  then  filled 
to  the  mark  with  distilled  water.  The  respective  volumes 
of  iodin  and  starch  solution,  together  with  the  added  water, 
deducted  from  the  500  c.c.,  will  show  the  volume  of  water 
actually  titrated  by  iodin.  A  correction  should  be  made 
as  follows  for  the  excess  of  iodin  required  to  produce  the 
blue  color:  Five  c.c.  starch  solution  are  made  up  with 
distilled  water  to  500  c.c.,  iodin  run  in  until  the  color  matches 
that  in  the  test,  and  the  volume  of  iodin  solution  so  used 
subtracted  from  the  figure  obtained  in  the  first  titration. 

Hardness.  C03  in  Normal  Carbonates.— Waters  con- 
taining considerable  quantities  of  calcium  and  magnesium 
are  said  to  be  hard.  Since  the  solution  of  calcium  and 
magnesium  carbonate  in  water  depends  partly  upon  the 
presence  of  carbon  dioxid,  boiling  precipitates  the  greater 


9 6  ANALYTIC   OPERATIONS. 

portion  of  the  carbonates,  the  result  being  to  dimmish  the 
hardness — i.  e.,  to  soften  the  water.  Magnesium  and 
calcium  sulfates  and  chlorids  are  not  precipitated  in  this  way. 
Hardness,  therefore,  is  divided  into  two  classeSj  temporary 
and  permanent,  the  former  being  that  which  may  be  re- 
moved by  boiling.  The  determination  may  be  made  either 
by  titration  or  by  soap  solution. 

TITRATION  METHOD. — This  method  is  due  to  Hehner. 
Reagents  Required : 

Standard  Sodium  Carbonate. — 1.06  grams  of  recently 
ignited  pure  sodium  carbonate  are  dissolved  in  water  and 
the  solution  diluted  to  1000  c.c.  One  c.c.  =  0.00106  gram 
Na2CO3  equivalent  to  o.ooi  gram  CaCO3. 

Standard  Sulfuric  Acid. — One  c.c.  of  pure  concentrated 
sulfuric  acid  is  added  to  about  1000  c.c.  of  water.  Fifty 
c.c.  of  the  standard  sodium  carbonate  are  placed  in  a 
porcelain  dish,  heated  to  boiling,  a  few  drops  of  a  solution 
of  methyl  orange  added,  and  the  sulfuric  acid  cautiously 
run  in  from  a  buret  until  the  proper  change  of  color  occurs. 
From  the  figure  thus  obtained,  the  extent  to  which  the  acid 
should  be  diluted  in  order  to  make  i  c.c.  of  the  sodium 
carbonate  equivalent  to  i  c.c.  of  the  acid  may  be  calculated. 
The  proper  amount  of  water  is  then  added,  and  the  solution 
verified  by  again  titrating. 
Analytic  Process : 

Temporary  Hardness. — One  hundred  c.c.  to  250  c.c. 
of  the  water  tinted  with  the  indicator  are  heated  to  boil- 
ing, and  the  sulfuric  acid  cautiously  run  in  until  the  color- 
change  occurs.  Each  cubic  centimeter  required  will  repre- 
sent one  part  of  calcium  carbonate  or  its  equivalent  per 
100,000  parts  of  the  water. 


TECHNIC   EXAMINATIONS.  97 

Permanent  Hardness. — To  100  c.c.  of  the  water  is  added 
an  amount  of  the  sodium  carbonate  solution  more  than  suffi- 
cient to  decompose  the  calcium  and  magnesium  sulfates, 
chlorids,  and  nitrates  present;  usually  a  bulk 'equal  to  the 
water  taken  will  be  more  than  sufficient.  The  mixture 
is  evaporated  to  dryness  in  a  nickel  or  platinum  dish,  and 
the  residue  extracted  with  distilled  water.  The  solution 
is  filtered  through  a  very  small  filter,  and  the  filtrate  and 
washings  titrated  hot  with  sulfuric  acid  as  above;  or  25 
c.c.  of  distilled  water  may  be  poured  on  the  residue,  and 
the  solution  obtained  filtered  through  a  dry  filter,  the 
filtrate  measured  and  titrated.  The  difference  between 
the  number  of  cubic  centimeters  of  sodium  carbonate  used 
and  the  acid  required  for  the  residue  will  give  the  permanent 
hardness. 

If  the  water  contains  sodium  or  potassium  carbonate, 
there  will  be  no  permanent  hardness,  and  there  will  be 
more  acid  required  for  the  filtrate  than  the  equivalent  of 
the  sodium  carbonate  added.  From  this  excess  the  quan- 
tity of  sodium  carbonate  in  the  water  may  be  determined. 

Since  any  alkali  carbonate  in  the  water  would  be  erro- 
neously calculated  as  temporary  hardness  by  the  direct 
titration,  the  equivalent,  in  terms  of  calcium  carbonate,  of 
the  alkali  carbonate  present  should  be  deducted  from  the 
figure  given  by  the  titration  in  order  to  get  the  true  tem- 
porary hardness. 

The  total  CO3  in  normal  carbonates  is  given  by  the 
direct  titration  of  the  water  with  dilute  sulfuric  acid.  One 
c.c.  of  the  acid  is  equivalent  to  0.0006  gram  of  CO8. 

SOAP  METHOD. — Many  chemists  estimate  hardness  by 
the  use  of  soap  solution.  The  following  is  a  description 


98  ANALYTIC   OPERATIONS. 

of  this  method,  as  carried  out  in  the  laboratory  of  the 
Massachusetts  State  Board  of  Health: 
Reagents  Required : 

Standard  Calcium  Chlorid  Solution. — 0.2  gram  of  Ice- 
land spar  is  dissolved  in  dilute  hydrochloric  acid  in  a  por- 
celain dish,  the  solution  evaporated  to  dryness,  redissolved 
and  reevaporated,  until  a  perfectly  neutral  salt  remains. 
This  is  dissolved  in  water  and  made  up  to  one  liter.  One 
c.c.  contains  calcium  equivalent  to  0.0002  gram  calcium 
carbonate. 

Soap  Solution. — 0.50  gram  of  best  quality,  dry,  white, 
Castile  soap  is  cut  into  thin  shavings,  dissolved  in  a  mix- 
ture of  250  c.c.  of  96  per  cent,  alcohol  and  250  c.c.  of  dis- 
tilled water,  and  allowed  to  stand  overnight  to  settle;  50 
c.c.  of  the  clear  liquid  are  then  made  up  to  one  liter,  enough 
alcohol  being  used  to  keep  all  of  the  soap  in  solution. 
Fifty  c.c.  of  the  standard  solution  of  calcium  chlorid,  which, 
according  to  the  table,  should  take  exactly  14.25  c.c.  of 
standard  soap,  are  used  to  test  the  strength.  The  soap 
solution  thus  prepared  does  not  change  perceptibly  if 
air  has  no  access  to  it,  and,  if  used  with  a  siphon  buret  at- 
tached to  the  bottle,  will  keep  for  five  or  six  weeks  or  longer. 
It  contains  5.2  grams  of  Castile  soap  to  the  liter. 

For  the  standardization  of  the  soap,  and  for  the  deter- 
mination of  the  hardness  of  any  water,  50  c.c.  of  the  sample 
or  of  the  standard  calcium  chlorid  solution  are  placed  in  a 
flask  or  bottle  of  200  c.c.  capacity,  and  of  a  convenient 
shape,  and  the  soap  solution  added,  -f$  or  -f$  of  a  c.c.  at  a 
time,  shaking  well  after  each  addition,  until  a  lather  is 
obtained  which  is  permanent  for  five  minutes  and  covers  the 
entire  surface  of  the  liquid  with  the  bottle  placed  on  its  side. 


TECHNIC   EXAMINATIONS. 


99 


The  following  table  gives  the  hardness  corresponding  to 
the  number  of  cubic  centimeters  of  soap  solution  used  in 
the  analyses: 


C.C.   OF 

SOAP 

HARDNESS. 

SOLUTION 

0.7 

0.0 

0.8 

O.I 

0.9 

°-3 

.0 

0.4 

.1 

0.6 

.2 

0.7 

•3 

0.9 

•4 

i.i 

•5 

.2 

.6 

•4 

•7 

•5 

.8 

.6 

•9 

.8 

2.0 

•9 

2.1 

2.O 

2.2 

2.2 

2-3 

2-3 

2.4 

2.4 

2-5 

2.6 

2.6 

2-7 

2.7 

2.8 

2.8 

2.9 

2.9 

3-1 

3-° 

3-2 

3.1 

3-3 

3-2 

3-5 

3-3 

3-6 

3-4 

3-7 

3-5 

3-9 

3-6 

4.0 

C.C.   OF 

C.C.   OF 

SOAP 

HARDNESS. 

SOAP    H, 

VRDNESS. 

SOLUTION 

SOLUTION. 

3-7 

4.1 

6.7 

8-4 

3-8 

4.2 

6.8 

8-5 

3-9 

4-4 

6.9 

8.7 

4.0 

4-5 

7.0 

8.8 

4.1 

4-7 

7.1 

9.0 

4.2 

4-8 

7.2 

9.1 

4-3 

5.0 

7-3 

9.2 

4-4 

5.1 

7-4 

9.4 

4-5 

5-2 

7-5 

9-5 

4.6 

5-4 

7.6 

9-7 

4-7 

5-5 

7-7 

9.8 

4-8 

5-7 

7-8 

IO.O 

4-9 

5-8 

7-9 

IO.I 

6.0 

8.0 

10.3 

5-1 

6-.  i 

8.1 

10.4 

5-2* 

6.2 

8.2 

10.6 

5-3 

6.4 

8-3 

10.7 

5-4 

6-5 

8.4 

10.9 

5-5 

6.7 

8-5 

II.O 

5-6 

6.8 

8.6 

II.  2 

5-7 

7.0 

8-7 

n-3 

5-8 

8.8 

5-9 

7-2 

8.9 

1  1.  6 

6.0 

7-4 

9.0 

11,8 

6.1 

7-5 

9.1 

11.9 

6.2 

7-7 

9.2 

12.  1 

6-3 

7-8 

9-3 

12.2 

6.4 

8.0 

9-4 

12.4 

6-5 

8.1 

9-5 

I2-5 

6.6 

8.2 

The  soap  solution  must  be  added  in  small  quantities, 
especially  in  the  presence  of  magnesium  compounds.  If 
much  carbonic  acid  be  liberated,  it  is  well  to  remove  it  by 
suction.  The  table  given  above  does  not  apply  to  hard- 
ness above  12.5.  If  the  water  tested  requires  more  than 


100  ANALYTIC   OPERATIONS. 

10  c.c.  of  the  standard  soap  solution,  a  smaller  portion  of 
25  c.c.,  10  c.c.,  or  even  2  c.c.,  as  the  case  may  require, 
is  measured  out  and  made  up  to  a  volume  of  50  c.c.  with 
recently  distilled  water.  This  will  keep  the  results  com- 
parable with  each  other,  although  the  dilution  introduces 
some  error  into  the  calculation. 

If  the  hardness  of  a  water  is  given  as  9.0,  it  means  that 
in  100,000  pounds  of  water  there  is  of  calcium  and  mag- 
nesium salts  a  quantity  which  gives  the  same  hardness  to 
water  which  would  be  given  by  nine  pounds  of  calcium 
carbonate.  In  order  to  soften  this  water  for  manufacturing 
purposes,  about  nine  pounds  of  soda  ash  will  be  required, 
and  for  laundry  purposes  about  ninety  pounds  of  soap. 

Free  and  Half-bound  Carbonic  Acid. — Several  methods 
for  the  determination  of  these  data  have  been  devised. 
Pettenkofer's  is  much  used,  but  F.  B.  Forbes  and  G.  H. 
Pratt,  after  careful  study  of  different  methods,  favor  the 
Lunge-Trillich  (also  termed  the  Seyler)  method,  which 
they  describe  as  follows: 

One  hundred  c.c.  of  the  sample  are  placed  in  a  tall  glass 
cylinder,  by  means  of  a  siphon  (in  order  to  avoid  contact 
with  air),  6  drops  of  neutral  alcoholic  solution  of  phenol- 
phthalein  added,  and  -f$  sodium  carbonate  run  in  from  a 
buret  with  careful  stirring,  until  a  faint  permanent  pink 
is  obtained.  If  the  water  contains  much  free  carbonic 
acid,  it  is  better  to  take  less  than  100  c.c.,  and  in  every  case 
care  must  be  taken  not  to  stir  the  sample  so  vigorously  as 
to  cause  loss  of  the  acid,  nor  to  proceed  so  slowly  that  it 
may  be  absorbed  from  the  air.  The  solutions  must  be 
carefully  standardized  and  preserved  so  that  they  do  not 
absorb  the  acid.  The  fixed  carbonic  acid  is  determined  on 


TECHNIC   EXAMINATIONS.  IOI 

another  portion  of  the  sample  by  Hehner's  method  as 
given  above.  .  In  waters  acid  to  phenolphthalein  this  will 
be  equal  to  the  half-bound. 

When  the  water  is  alkaline  to  phenolphthalein,  the 
alkalinity  with  this  indicator  is  first  determined,  then  the 
total  alkalinity  by  Hehner's  method.  Twice  the  phenol- 
phthalein alkalinity  subtracted  from  the  total  alkalinity 
gives  the  half-bound  acid,  no  free  acid  being  present  in 
this  case,  and  the  half -bound  being  less  than  the  fixed. 
If  the  water  is  neutral  to  phenolphthalein,  the  half-bound 
may  be  equal  to  the  fixed. 

Forbes  and  Pratt  have  modified  the  Pettenkofer  methods 
as  follows: 

Ground  glass-stoppered  bottles,  holding  approximately 
480  c.c.,  are  accurately  calibrated  by  weighing  completely 

filled  with  water.     The  bottle  is  filled  with  the  water  to  be 
f  ^       . 

analyzed  by  means  of  a  siphon,  the  glass  stopper  inserted, 
leaving  no  air-bubble,  and  the  neck  of  the  bottle  wiped  dry. 
The  glass  stopper  is  then  carefully  removed,  and  the  57 
c.c.  of  the  water  withdrawn  by  means  of  an  accurately 
calibrated  pipet,  in  order  to  make  room  for  the  reagents. 
Three  c.c.  of  strong  barium  chlorid  solution  (8  grams  per 
liter),  2  c.c.  of  saturated  ammonium  chlorid  solution,  and 
50  c.c.  of  standard  barium  hydro xid  are  then  introduced, 
the  bottle  quickly  stoppered,  well  shaken,  and  set  aside 
to  settle. 

There  is  now  in  the  bottle  an  air  space  of  only  2  c.c., 
which  is  left  to  avoid  the  possibility  of  loss  of  liquid  when 
the  stopper  is  inserted.  After  the  precipitated  carbonates 
have  completely  settled  out,  several  portions  of  100  c.c.  are 
siphoned  off  and  titrated  with  -£$  sulfuric  acid,  which  is 


102  ANALYTIC    OPERATIONS. 

prepared  from  decinormal  acid,  against  which  the  barium 
hydroxid  is  standardized,  by  carefully  diluting  with  water 
freed  from  carbonic  acid  by  boiling.  The  barium  hydroxid 
that  we  use  is  approximately  TN^-,  and  is  carefully  pre- 
served out  of  contact  with  the  air,  the  bottle  in  which  it  is 
kept  being  fitted  with  an  arrangement  whereby  the  air  is 
drawn  through  soda-lime  before  entering  either  the  bottle 
or  the  buret.  The  figure  obtained  by  averaging  several 
results  of  titration  of  portions  of  100  c.c.  is  taken  as  the  true 
value. 

The  use  of  this  large  quantity  of  water  and  the  titration 
of  100  c.c.  portions  reduce  considerably  the  errors  due  to 
the  difficulty  of  obtaining  the  exact  end-point,  and  those 
due  to  inaccuracies  of  measurement. 

Boric  Acid. — To  detect  it,  add  to  one  liter  of  the  water 
sufficient  sodium  carbonate  to  render  it  distinctly  alkaline. 
Evaporate  to  dryness,  acidify  with  hydrochloric  acid, 
moisten  a  slip  of  turmeric  paper  with  the  liquid,  and  dry 
it  at  a  moderate  heat.  In  the  presence  of  boric  acid  the 
paper  will  assume  a  distinct  brown-red  tint. 

Analysis  of  Boiler  Scale. — If  the  scale  is  made  up  of 
pieces  of  decidedly  different  quality,  some  being  hard  and 
gritty,  others  soft  and  friable,  separate  tests  should  be 
made  on  representative  samples  of  each  sort;  but  if  the 
general  character  is  fairly  uniform,  it  will  be  sufficient  to 
sample  the  entire  mass  and  reduce  about  5  grams  to  a  fine 
powder,  finishing  in  an  agate  mortar.  All  of  the  quantity 
selected  as  the  sample  should  be  equally  finely  powdered. 

0.5  gram  should  be  heated  in  a  covered  beaker  with 
moderately  strong  hydrochloric  acid,  until  all  soluble 
matter  is  dissolved ;  the  liquid  is  then  evaporated  to  dryness 


TECHNIC   EXAMINATIONS. 


I03 


on  the  water-bath,  redissolved  in  water  containing  some 
hydrochloric  acid,  and  filtered.  The  precipitate  is  silica. 
The  nitrate  and  washings  are  mixed  and  divided  into 
convenient  parts.  One  part  is  used  for  the  determination  of 
sulfates,  and  the  other  for  iron  oxid,  alumina,  calcium,  and 
magnesium,  according  to  the 
methods  given  on  pages  87 
to  90.  Scale  often  contains  an 
appreciable  amount  of  oil. 
This  may  be  determined  by 
extracting  a  known  weight  of 
the  fully  produced  material 
with  a  petroleum  spirit  that 
leaves  no  residue  on  evapora- 
tion on  the  water-bath. 

SPECTROSCOPIC  EXAMI- 
NATION. 

For  the  ordinary  spectro- 
scopic  examination  of  a  water 
a  simple  apparatus  will  suf- 
fice. The  arrangement  shown 
in  the  cut  (Fig.  13)  is  a  small 
direct-vision  spectroscope, 
held  in  a  universal  stand, 
with  an  adjustable  burner  as 
the  source  of  heat. 

For  the  examination  a  liter  or  more  should  be  evaporated 
nearly  to  dryness,  a  little  hydrochloric  acid  being  added 
near  the  end  of  the  process,  the  residue  placed  in  a  narrow 
strip  of  platinum  foil,  having  the  sides  bent  so  as  to  retain 


FIG.  13. 


104  ANALYTIC   OPERATIONS. 

the  liquid,  and  heated  in  the  flame.  While  this  method 
will,  be  sufficient  in  many  cases,  a  far  better  plan  is  to 
separate  the  substance  sought  for  in  a  state  of  approximate 
purity  and  then  examine  with  the  spectroscope.  Very 
small  traces  of  lithium,  for  instance,  may  be  detected  as 
follows:  To  about  a  liter  of  the  water  sufficient  sodium 
carbonate  is  added  to  precipitate  all  the  calcium  and  mag- 
nesium, and  the  liquid  boiled  down  to  about  one-tenth  its 
bulk;  it  is  then  filtered,  the  filtrate  rendered  slightly  acid 
with  hydrochloric  acid,  and  evaporated  to  dryness.  The 
residue  is  boiled  with  a  little  alcohol,  which  will  dissolve 
out  the  lithium  chlorid.  The  alcoholic  solution  is  evapo- 
rated to  dryness,  the  residue  taken  up  with  a  little  water 
and  tested  in  the  flame. 

In  order  to  identify  with  certainty  any  line  which  may 
be  obtained,  it  is  only  necessary  to  hold  in  the  flame  at 
the  same  time  a  wire  which  has  been  dipped  in  a  solution 
of  the  substance  supposed  to  be  present  and  to  note  whether 
the  lines  produced  by  it  and  the  material  under  examination 
are  identical. 

SPECIFIC  GRAVITY. 

In  the  great  majority  of  cases  the  determination  of 
specific  gravity  is  not  essential.  Ordinary  river,  spring, 
and  well  waters  contain  such  small  proportions  of  solid 
matter  that  it  is  usually  the  practice  to  take  a  measured 
volume  and  to  assume  its  weight  to  be  that  of  an  equal 
bulk  of  pure  water.  If  the  proportion  of  solids  be  high,  a 
determination  of  the  specific  gravity  may  be  desirable. 
For  this  purpose  the  specific  gravity  bottle  may  be  used. 
This  consists  merely  of  a  small  flask  provided  with  a  finely 


TECHNIC    EXAMINATIONS.  105 

perforated  glass  stopper.  The  bottle  is  weighed  first  alone, 
then  filled  with  distilled  water  at  60°  F.,  and  finally  with 
the  water  under  examination  at  the  same  temperature.  In 
filling  the  bottle,  the  liquid  is  first  brought*  to  the  proper 
temperature,  the  bottle  completely  filled,  the  stopper  in- 
serted, and  the  excess  of  water  forced  out  through  the 
perforation  and  around  the  sides  of  the  stopper  carefully 
removed  by  bibulous  paper.  The  weight  of  the  water 
examined  divided  by  the  weight  of  the  equal  bulk  of  dis- 
tilled water  at  the  same  temperature  gives  the  specific 
gravity. 

Another  method,  and  one  which  gives  very  satisfactory 
results,  is  by  the  use  of  a  plummet.  This  may  conveniently 
consist  of  a  piece  of  a  thick  glass  rod  of  about  10  c.c.  in 
bulk,  or  of  a  test-tube  weighted  with  mercury  and  the  open 
end  sealed  in  the  flame.  The  plummet  is  suspended  to  the 
hook  of  the  balance  by  means  of  a  fine  platinum  wire  and 
its  weight  ascertained.  It  is  then  immersed  in  distilled 
water  at  60°  F.,  and  the  loss  in  weight  noted.  The  figure 
so  obtained  is  the  weight  of  a  bulk  of  water  equal  to  that 
of  the  plummet.  This  having  been  determined,  the  specific 
gravity  of  any  water  may  be  found  by  immersing  in  it  the 
plummet  and  noting  the  loss  in  weight.  This,  divided  by 
the  loss  suffered  in  pure  water,  gives  the  specific  gravity. 


INTERPRETATION    OF    RESULTS. 

STATEMENT  OF  ANALYSIS. 

The  composition  of  water  is  generally  expressed  in  terms 
of  a  unit  of  weight  in  a  definite  volume  of  liquid,  but  much 
difference  exists  as  to  the  standard  used.  The  decimal 
system  is  very  largely  employed,  the  proportions  being 
expressed  in  milligrams  per  liter,  nominally  parts  per  mil- 
lion ;  or  in  centigrams  per  liter,  nominally  parts  per  hundred 
thousand.  The  figures  are  often  given  in  grains  per  im- 
perial gallon  of  70,000  grains,  or  the  U.  S.  gallon  of  58328 
grains.  In  this  work  the  composition  is  always  expressed 
in  milligrams  per  liter.  This  ratio  is  practically  equivalent 
to  parts  per  million,  except  in  case  of  water  very  rich  in 
solids,  a  liter  of  which  will  weigh  notably  more  than  one 
million  milligrams.  Factors  for  converting  the  different 
ratios  are  given  at  the  end  of  the  book. 

From  the  analysis  of  a  water  it  is  rarely  possible  to  ascer- 
tain the  exact  arrangement  of  the  elements  determined,  but 
it  is  the  custom  to  assume  arrangements  based  upon  the 
rule  of  associating  in  combination  elements  having  the 
highest  affinities,  modifying  this  system  by  any  inferences 
derived  from  the  character  or  reactions  of  the  water  itself. 
It  has  been  demonstrated  that,  even  in  the  case  of  mixtures 
of  salts  producing  no  insoluble  substances,  partial  inter- 
change of  the  basylous  and  acidulous  radicles  takes  place. 
In  a  solution  of  sodium  chlorid  and  potassium  sulfate 

106 


SANITARY  APPLICATIONS.  1 07 

sodium  sulfate  and  potassium  chlorid  will  be  found,  as 
well  as  the  original  salts.  When  the  conditions  are  ren- 
dered more  complex  by  the  addition  of  other  substances, 
it  is  obviously  impossible  to  determine  the  exact  arrange- 
ment. In  view  of  these  facts,  it  is  preferable  to  express 
the  composition  of  a  water  by  the  proportion  of  each  ele- 
ment or  radicle  present.  In  this  way  a  water  containing 
K2SO4  will  be  expressed  in  terms  of  K  and  SO4,  respec- 
tively. In  the  case  of  bodies  like  CO2  and  SiO2,  which 
may  possibly  exist  free  in  the  water,  their  proportion  is 
expressed  as  such.  It  frequently  occurs  that  the  character- 
istics of  some  of  the  compounds  in  a  water  are  sufficiently 
marked  to  indicate  their  presence,  and  there  can  be  no 
objection  to  suggesting,  in  connection  with  the  analytic 
statement,  the  inferences  which  may  thus  be  drawn. 

The  organic  matters,  or  derived  products,  are  best 
stated  in  terms  of  the  nitrogen  which  they  contain,  thus 
permitting  a  comparison  of  the  different  stages  of  decom- 
position. It  is  inadvisable  to  represent  the  amount  of 
unchanged  organic  matter  in  terms  of  oxalic  acid,  as  has 
been  suggested,  or  to  express  the  nitrogen  in  terms  of 
albumin,  or  any  other  supposititious  compound. 

The  results  of  bacteriologic  examinations  should,  as  a 
rule,  be  reported  as  "points  of  microbic  life"  in  the  given 
volume  of  water.  Many  operators,  however,  report  the 
number  of  points  as  "colonies"  or  even  "bacteria." 

SANITARY  APPLICATIONS. 

Judgment  upon  the  analytic  results  from  a  given  sam- 
ple of  water  depends  upon  the  class  to  which  it  belongs, 
and  to  the  particular  influences  to  which  it  has  been  sub- 


108          INTERPRETATION  OF  RESULTS. 

jected.  A  proportion  of  total  solids  which  would  be  sus- 
picious in  a  rain  or  river  water,  would  be  without  signifi- 
cance in  that  from  an  artesian  well.  On  the  other  hand,  a 
subsoil  water  of  unobjectionable  character  would  contain  a 
proportion  of  nitrates  which  would  be  inadmissible  in  the 
case  of  a  river  or  deep  water.  Location  has  also  much 
bearing  in  the  case;  subsoil  waters  near  the  sea  will  be 
found  to  contain,  without  invoking  suspicion,  proportions 
of  chlorin  which  would  be  ample  to  condemn  the  same 
sample  if  derived  from  a  point  far  inland.  Hence  the  im- 
portance of  recording,  at  the  time  of  collection,  all  ascer- 
tainable  information  as  to  the  surroundings  and  probable 
source  of  the  water. 

Analyses  of  surface  waters  have  little  value,  unless  sup- 
plemented by  a  careful  survey  of  the  watershed  to  deter- 
mine sources  of  pollution.  Such  survey  will  often  discover 
conditions  sufficient  to  condemn  the  supply,  even  though 
the  analyses  may  be  satisfactory.  Indeed,  it  may  be  taken 
as  a  fundamental  principle  that  surface  water  from  even 
a  sparsely  populated  district  will  be  unsafe  for  use  unless 
efficiently  filtered. 

Color,  Odor,  and  Taste. — Water  of  the  highest  purity 
will  be  clear,  colorless,  odorless,  and  nearly  tasteless. 
While  in  some  cases  a  decided  departure  from  this  stand- 
ard may  give  rise  to  suspicion,  analytic  observations  are 
necessary  to  decide  the  point.  Water  highly  charged  with 
mineral  matters  will  possess  decided  taste,  vegetable 
matters  may  communicate  distinct  color;  but,  on  the  other 
hand,  it  may  be  highly  contaminated  with  dangerous  sub- 
stances and  give  no  indications  to  the  senses.  Well- 
waters  occasionally  become  offensive  in  odor,  from  pene- 


SANITARY  APPLICATIONS.  1 09 

tration  of  tree  roots.  The  odor  often  recalls  that  of 
hydrogen  sulfid.  Sulfids  are,  indeed,  often  formed  in  such 
cases  by  the  abstraction  of  oxygen  from  sulfates  under 
the  influence  of  microbes.  Such  waters  are  often  used 
without  apparent  injury,  but  it  is  probable  that  if  direct 
pollution  occurs,  the  danger  would  be  enhanced  by  the 
presence  of  the  vegetable  matter. 

Surface  waters  collected  in  reservoirs  or  ponds  often 
become  very  offensive  from  the  growth  of  algae,  but  apart 
from  the  disgust  created  by  the  water,  it  is  not  known  that 
any  harmful  results  occur  to  those  using  it. 

Turbidity  may  be  due  to  several  causes,  of  different 
degrees  of  danger,  but  is  always  objectionable. 

Total  Solids. — Excessive  proportions  of  mineral  solids, 
especially  of  marked  physiologic  action,  are  known  to 
render  water  non-potable,  but  no  absolute  maximum  or 
minimum  can  be  assigned  as  the  limit  of  safety.  Dis- 
tilled water  and  waters  very  highly  charged  with  mineral 
matter  have  been  used  for  long  periods  without  ill  effects. 
The  popular  notion  that  the  so-called  hard  waters  con- 
duce to  the  formation  of  urinary  calculi  is  not  borne  out 
by  surgical  experience  or  statistical  inquiry.  Many  urinary 
calculi  are  composed  of  uric  acid,  and  are  the  results  of 
disorders  of  the  general  nutritive  functions. 

Sanitary  authorities  have  fixed  an  arbitrary  limit  of  total 
solids  of  about  six  hundred  parts  per  million,  but  many 
artesian  waters  in  constant  use  exceed  this.  An  instance 
is  found  in  the  well  on  Black's  Island,  near  Philadelphia, 
which  contains  nearly  twelve  hundred  parts  per  million, 
is  very  agreeable  in  taste,  and  has  been  in  constant  use  for 
some  years  by  a  number  of  persons  without  injury.  The 


110  INTERPRETATION  OF  RESULTS. 

assertion  that  water  to  be  wholesome  must  contain  an 
appreciable  proportion  of  total  solids  is  also  not  demon- 
strated by  clinical  experience.  A  discussion  of  the  effects 
of  special  mineral  ingredients — e.  g.,  magnesium  sulfate, 
ferrous  carbonate,  etc. — belongs  to  general  therapeutics. 

The  odor  produced  on  heating  the  water  residue  is  often 
of  much  use  in  detecting  contamination.  Odors  similar 
to  those  produced  by  heating  glue,  hair,  rancid  fats,  urine, 
or  other  animal  products,  will  give  rise  to  grave  suspicion. 
On  the  other  hand,  a  more  favorable  judgment  may  be 
given  when  the  odor  recalls  those  given  off  in  the  heating 
of  non-nitrogenous  vegetable  materials,  such  as  wood-fiber. 

Poisonous  Metals. — The  proportion  of  iron  in  water 
constantly  used  for  drinking  purposes  should  not  much 
exceed  three  parts  per  million.  Lead,  copper,  arsenic, 
and  zinc  must  be  considered  dangerous  in  any  amount, 
though  it  appears  that  zinc  and  copper,  being  least  cumu- 
lative, are  rather  less  objectionable  in  minute  amount  than 
the  others.  Concerning  the  limit  of  safety  with  mangan- 
ese and  chromium  very  little  is  known,  but  their  presence 
in  appreciable  quantity  must  be  looked  upon  with  suspicion. 

Chlorids  and  Phosphates. — Chlorids — principally  so- 
dium chlorid — and  phosphates  are  abundantly  distributed 
in  rocks  and  soils,  and  find  their  way  into  natural  waters; 
but  while  the  former  are  freely  soluble  and  remain  in  un- 
diminished  amount  under  all  conditions  to  which  the  water 
is  subjected,  all  but  small  amounts  of  the  latter  are  either 
precipitated  or  removed  by  the  action  of  living  organisms. 
Surface  and  subsoil  waters  ordinarily  contain  but  a  few 
parts  per  million.  Both  chlorids  and  phosphates  being 
constant  and  characteristic  ingredients  of  animal  excre- 


SANITARY  APPLICATIONS.  Ill 

tions,  it  is  obvious  that  an  excess  of  them  in  natural  waters, 
unless  otherwise  accounted  for,  will  suggest  direct  con- 
tamination. Proximity  to  localities  in  which  sodium  chlorid 
is  abundant,  such  as  the  sea-  or  salt-deposits,  will  deprive 
the  figure  for  the  chlorin  of  diagnostic  value,  nor  can  any 
indication  of  sewage  or  other  dangerous  pollution  be  in- 
ferred from  high  proportion  of  chlorin  in  deep  waters. 
Further,  it  has  be.en  shown  that  the  proportion  of  chlorin 
in  uncontaminated  waters  is  tolerably  constant,  while 
in  water  subjected  to  the  infiltration  of  sewage  the  chlorin 
undergoes  marked  variation  in  amount.  In  most  cases, 
therefore,  a  correct  judgment  can  only  be  attained  by  com- 
parison with  the  average  character  of  the  waters  of  the 
same  type  in  the  district,  and  by  examination  at  intervals 
of  the  water  in  question. 

As  regards  phosphates,  Hehner,  who  has  published  a 
series  of  analyses,  states  mat  the  presence  of  more  than  0.6 
part  per  million — calculated  as  PO4 — should  be  regarded 
with  suspicion.  On  the  other  hand,  the  absence  of  phos- 
phates affords  no  positive  proof  of  the  freedom  from  pol- 
lution. Woodman,  who  has  carefully  investigated  this 
question,  regards  Hehner's  limit  as  too  strict.  He  would 
fix  i  part  per  million  as  the  minimum.  He  regards  this 
datum  as  valuable  in  judging  of  the  sanitary  quality  of 
the  sample. 

Nitrogen  from  Ammonium  Compounds. — Ammonium 
compounds  are  usually  the  results  of  the  putrefactive  fer- 
mentation of  nitrogenous  organic  matter;  they  may  also 
be  the  product  of  the  reduction  of  nitrites  and  nitrates 
in  presence  of  excess  of  organic  matter.  In  either  case, 
therefore,  they  suggest  contamination.  Deep  waters  often 


112          INTERPRETATION  OF  RESULTS. 

contain  an  excess  of  ammonium  compounds,  derived,  in 
large  part,  from  the  reduction  of  nitrates.  Their  presence 
here  is  hardly  ground  for  adverse  judgment,  since  the 
water,  even  though  originally  contaminated,  has  undergone 
extensive  nitration  and  oxidation,  its  organic  matter  con- 
verted into  bodies  presumably  harmless,  and  microbes  have 
perished.  Such  waters,  indeed,  usually  show  only  traces 
of  unchanged  organic  matter. 

Rain  water  often  contains  large  proportions  of  ammo- 
nium compounds;  but  here,  also,  the  fact  can  not  condemn 
the  water,  since  it  does  not  indicate  contamination  with 
dangerous  organic  matter. 

The  evolution  of  ammonia  in  the  distillation  of  rain  water 
may  continue  indefinitely,  the  larger  portion  passing  over 
in  the  first  distillates,  but  small  quantities  being  present 
even  after  the  distillation  has  been  much  prolonged.  The 
same  continuous  evolution  of  ammonia  has  been  noted  in 
waters  containing  urea,  but  in  this  case  a  larger  proportion 
is  collected  in  the  earlier  distillates,  nearly  all  coming  over 
before  one-half  the  water  has  been  distilled. 

Nitrogen  by  Alkaline  Permanganate  (Nitrogen  of 
" albuminoid  ammonia"). — A  large  yield  of  ammonia 
by  boiling  with  alkaline  potassium  permanganate  will,  of 
course,  point  to  an  excess  of  nitrogenous  organic  matter. 
The  inferences  to  be  drawn  depend  upon  the  origin  and 
condition  of  the  organic  material.  If  animal,  the  water 
may  at  once  be  condemned  as  unsafe.  Waters  containing 
excessive  amounts  even  of  vegetable  matter  are  not  free 
from  objection,  since  they  have  frequently  caused  persis- 
tent diarrhea.  If  the  organic  matter,  whether  animal  or 
vegetable,  is  in  a  state  of  active  decomposition,  it  is  doubly 


SANITARY  APPLICATIONS.  113 

objectionable.  Mallet  has  called  attention  to  the  fact 
that  such  waters,  as  a  rule,  yield  ammonia  rapidly,  whereas 
non-decomposing  material  yields  it  but  slowly,  and  he 
points  out  the  importance,  therefore,  of  notirrg  the  rate  at 
which  the  ammonia  collects  in  the  distillate. 

Smart  has  observed  that  water  containing  fermenting 
vegetable  matter  is  colored  yellow  by  boiling  with  sodium 
carbonate. 

Inferences  as  to  the  source  of  the  organic  matter  can 
usually  be  drawn  from  the  amount  of  chlorin  and  nitrates 
present.  If  the  chlorin  be  high, — i.  e.,  in  excess  of  the 
average  of  the  district, — it  may  be  inferred  that  the  mate- 
rial is,  in  great  part,  of  animal  origin.  In  this  case  the 
nitrates  will  either  be  high  or  entirely  absent,  according  as 
the  contaminating  matter  has  passed  through  soil  or  enters 
the  water  directly. 

A  large  amount  of  vegetable  matter  will,  as  a  rule,  show 
itself  by  the  color  it  imparts  to  the  water. 

Total  Nitrogen. — Drown  and  Martin's  results  with 
surface  waters  indicate  that  the  total  nitrogen  obtained  by 
their  process  is  about  twice  that  obtained  by  alkaline  per- 
manganate. The  experiments  made  by  Dr.  Beam  and  my- 
self accord  with  this.  Further  observation  on  different 
waters  and  by  different  observers  will  be  required  to  deter- 
mine the  value  to  be  assigned  to  the  figures  obtained  by 
this  method.  This  method  is  especially  suitable  for  study- 
ing the  effects  of  nitration,  storage,  etc.,  on  the  nitrogenous 
organic  matter  in  water. 

Nitrogen  as  Nitrites.— Nitrites  are  present  in  water 
as  the  result  either  of  incomplete  nitrification  of  ammo- 
nium, or  the  reduction  of  already  formed  nitrates,  under 


114          INTERPRETATION  OF  RESULTS. 

the  influence  of  reducing  agents  or  microbes.  Since  they 
are  transition  products,  their  presence  in  water  is  usually 
evidence  of  existing  fermentative  changes,  and,  further, 
may  be  taken  as  indicating  that  the  water  is  unable  to 
dispose  of  the  organic  contamination.  When,  however, 
the  conditions  are  such  that  oxidation  can  not  take  place, 
nitrites  may  persist  for  a  long  time.  This  sometimes 
occurs  in  deep  waters  in  which  fermentative  changes  have 
long  since  ceased,  but  oxygen  is  not  available.  These 
contain  not  infrequently  small  amounts  of  nitrites,  to 
which  the  same  degree  of  suspicion  can  not  be  attached. 
When  nitrites  are  found  in  these  waters,  the  possibility  of 
their  introduction  from  polluted  subsoil  water,  through 
defective  tubing,  must  not  be  overlooked.  Rain  water, 
also,  sometimes  contains  nitrites  derived  from  the  air,  and 
therefore  not  indicative  of  any  putrefactive  change.  The 
presence  of  measurable  quantities  of  nitrites  in  river  or 
subsoil  water  is  sufficient  ground  for  condemnation. 

Nitrogen  as  Nitrates. — Nitrates  are  the  final  point  in 
the  oxidation  of  nitrogenous  organic  matter,  especially 
animal  matters.  Rain  water  and  that  from  mountain 
streams  and  deep  wells,  except  from  cretaceous  strata, 
generally  contain  only  traces,  but  river  and  subsoil  waters 
will  always  contain  appreciable  amounts,  unless  some  re- 
ducing action,  such  as  recent  sewage -pollution,  is  at  work. 
When,  therefore,  a  water  contains  enough  mineral  matter 
to  demonstrate  its  percolation  through  soil,  and  at  the 
same  time  is  free  from  nitrates  or  contains  only  traces,  the 
occurrence  of  a  destructive  fermentation  may  be  inferred. 
These  cases  are  not  uncommon  among  well-waters,  and 
the  samples  are  generally  turbid  from  suspended  organic 


SANITARY  APPLICATIONS.  115 

matter.  Decided  departure,  either  by  increase  or  de- 
crease, from  the  proportion  of  nitrates  usual  in  the  same 
class  of  water  in  any  district  may  be  taken  as  evidence  of 
contamination. 

Oxygen-consuming  Power. — Sanitary  authorities  differ 
very  much  as  to  the  significance  of  this  datum.  Attempts 
have  been  made  to  fix  maximum  limits  for  the  various 
types  of  water,  and  also  to  gage  the  character  and  con- 
dition of  the  organic  matter  by  observing  the  rate  at  which 
the  oxidation  takes  place,  but  no  positive  conclusions  can 
be  given.  In  general,  it  may  be  said  that  a  sample  which 
has  'high  oxygen-consuming  power  will  be  more  likely 
to  be  unwholesome  than  one  which  is  low  in  this  respect; 
but  the  interferences  are  so  numerous,  and  the  suscep- 
tibility to  oxidation  of  different  organic  matters,  of  even 
the  same  type,  is  so  different,  that  the  method  is  at  best 
only  of  accessory  value. '  It  is  especially  suitable  for  con- 
secutive determinations  on  the  same  supply. 

The  following  proportions  are  given  by  Frankland  and 
Tidy  as  the  basis  of  interpreting  the  results  of  this  method: 

OXYGEN  ABSORBED  IN  THREE  HOURS. 

High  organic  purity, 0.05  parts  per  million. 

Medium  purity,    0.5    to  1.5     "       "         " 

Doubtful,   1.5    to  2.1      "       "         " 

Impure, over  2.1 

For  the  method  with  acidified  permanganate  at  the 
boiling  heat,  the  German  chemists,  who  employ  it  largely, 
regard  an  absorption  of  2.5  parts  of  oxygen  per  million 
as  suspicious,  and  some  sanitary  authorities  have  fixed  3.8 
parts  of  oxygen  per  million  as  the  highest  permissible  limit. 


n6 


INTERPRETATION   OF   RESULTS. 


Dissolved  Oxygen. — Full  aeration  of  water  is  favorable 
to  the  destruction  of  organic  matter;  a  decided  diminution 
in  the  quantity  of  dissolved  oxygen  may  show  excess  of 
such  matter  and  of  microbic  life.  Gerardin  has  pointed 
out  that  this  diminution  is  associated  with  the  development 
of  low  forms  of  vegetable  life,  and  Leeds  has  recorded 
similar  facts.  These  changes  are  more  likely  to  take  place 
in  still  waters,  and  are  frequently  accompanied  by  dis- 
agreeable odor  and  taste.  In  cases  in  which  stored  waters 
become  unpalatable,  these  facts  should  be  borne  in  mind. 

Hardness. — The  degree  of  hardness,  unless  very  high, 
has  but  little  bearing  on  the  sanitary  value  of  water,  but 
is  important  in  reference  to  its  use  for  general  household 
purposes,  in  view  of  the  soap-destroying  power  which  hard 
waters  possess. 

USUAL  ANALYTIC  RESULTS  FROM  UNCONTAMINATED  WATERS. 
Milligrams  pet'  Liter. 


RAIN. 

SURFACE. 

SUBSOIL. 

DEEP. 

Total  solids,  
Chlorin,    

5  to  20 
Traces  to  i 

15  upward 
i  to  10 

30  upward 
2  to  12 

45  upward 
Traces  to  large 

quantity 

Nitrogen      by     perman- 

ganate,      
Nitrogen  as  NH4,    .   .   . 
"    nitrites, 

0.08  to  0.20 

O.2O  tO  0.50 

None  or 

0.05  to  0.15 
o.oo  to  0.03 
None 

0.05  to  o.io 
o.oo  to  0.03 
None 

0.03  to  o.io 
Generally  high 
None  or  traces 

traces 

"   nitrates,     . 

Traces 

0.75  to  1.25 

i-5  to  5 

o.oo  to  3 

Inferences  from  Culture  Methods. — No  absolute  limit 
as  to  the  number  of  ordinary  microbes  can  be  fixed.  Some 
bacteriologists  have  fixed  the  maximum  of  100  per  cubic 
centimeter,  but  this  is  arbitrary.  An  appreciable  number 


ACTION   OF   WATER   ON   LEAD.  1 17 

of  microbes  of  the  intestinal  type  will  be  a  basis  for  con- 
demnation of  the  water. 

There  is,  however,  one  field  of  inquiry  in  which  even 
mere  microbe-counting  has  value;  that  is"  in  comparing 
samples  of  the  same  water  before  and  after  some  treatment 
or  other  incident.  In  these  studies  the  method  is  suffi- 
ciently free  from  fallacy  to  make  the  results  trustworthy 
when  they  are  conducted  in  a  strictly  uniform  manner; 
thus,  if  a  river  water  supplied  to  a  filter  be  studied  daily 
by  examination  of  repeated  samples  before  and  after  filtra- 
tion, inoculating  separate  portions  of  the  same  culture- 
medium,  and  multiplying  the  results  to  such  an  extent  as 
to  eliminate  accidental  differences,  a  comparison  between 
the  water  before  and  after  filtration  may  be  safely  made  as 
to  the  proportion  of  microbes  removed.  Moreover,  special 
microbes  of  highly  characteristic  properties  may  be  intro- 
duced in  large  quantities  into  the  water,  and  by  subse- 
quent culture  the  extent  to  which  these  are  removed  may 
be  satisfactorily  recognized. 

ACTION  OF  WATER   ON   LEAD. 

The  almost  universal  use  of  lead  pipes  for  conveying 
water,  and  the  facility  with  which  some  waters  corrode 
and  dissolve  the  metal,  make  it  a  question  of  moment  to 
determine  the  cause  of  this  action  and  to  devise  means  for 
its  prevention.  The  subject  has  received  considerable 
attention  within  the  last  few  years,  and  the  conditions  which 
determine  corrosion  are  now  fairly  understood.  As  a  rule, 
it  is  found  that  waters  free  from  mineral  matter  dissolve 
lead  with  facility,  especially  in  the  presence  of  oxygen. 
Some  very  soft  waters  are  entirely  without  action,  and 


Il8  INTERPRETATION  OF  RESULTS. 

this  was  unexplained  until  a  few  years  ago,  when  Messrs. 
Crookes,  Odling,  and  Tidy  found  that  the  action  was  con- 
trolled by  the  amount  of  silica  contained  in  the  water. 
They  found  that  those  soft  waters  which,  when  taken  from 
the  service  pipes,  contained  a  notable  quantity  of  lead, 
gave,  on  the  average,  three  parts  of  silica  per  million;  in 
those  in  which  there  was  no  lead,  the  silica  present  amounted 
to  7.5  per  million,  and  in  those  in  which  the  action  was 
intermediate,  5.5  parts  per  million.  That  it  was  really 
the  silica  that  conditioned  the  corrosion  was  confirmed  by 
laboratory  experiments.  They  also  found  that  the  most 
effective  way  of  silicating  a  water  is  by  passing  it  over  a 
mixture  of  flint  and  limestone.  The  reason  for  this  was 
pointed  out  later  by  Messrs.  Camelry  and  Frew,  who 
showed  that  while  calcium  carbonate  and  silica  both  exert 
a  protective  influence,  calcium  silicate  is  more  effective 
than  either;  and,  further,  that  in  almost  all  cases  in  which 
corrosion  took  place,  it  was  greater  in  the  presence  of 
oxygen.  This  is  particularly  the  case  with  potassium 
and  ammonium  nitrates  and  with  calcium  hydroxid.  The 
reverse  is  true  of  calcium  sulfate,  which  is  more  corrosive 
when  air  is  excluded.  Their  experiments  also  show  that 
the  presence  of  calcium  carbonate  or  calcium  silicate, 
altogether  prevents  corrosion  by  potassium  and  ammonium 
nitrates. 

As  the  result  of  an  elaborate  series  of  experiments,  Miiller 
concludes,  that  while  chlorids,  nitrates,  and  sulfates  all 
act  upon  lead  pipes,  no  corrosion  takes  place  in  the  pres- 
ence of  sodium  acid  carbonate,  and  that  calcium  car- 
bonate, by  taking  up  carbonic  acid,  acts  in  the  same  way. 
This  latter  conclusion  is  at  variance  with  the  observations 


TECHNIC   APPLICATIONS.  IIQ 

of  Carnelly  and  Frew,  who  found  that  calcium  carbonate 
is  equally  effective  when  carbonic  acid  is  excluded.  Mliller 
also  states  that  surface  waters,  contaminated  by  sewage 
and  containing  large  amounts  of  ammoniacal  compounds, 
will  dissolve  lead  under  all  circumstances. 

Allen  has  shown  that  water  containing  free  acid,  in- 
cluding sulfuric  acid,  acts  energetically  upon  lead.  This 
is  not  surprising  in  view  of  the  later  experiments,  which 
prove  that  even  calcium  sulfate  is  corrosive.  Later,  W. 
Carleton- Williams  found  that  even  in  the  presence  of  free 
acid,  corrosion  may  be  prevented  by  the  addition  of  suffi- 
cient silica.  His  experiments  also  confirm  the  view  gener- 
ally held,  that  soluble  phosphates  protect  lead  to  a  marked 
degree. 

The  following  is  a  summary  of  the  more  important  ob- 
servations on  this  subject: 

Corrosive:  Free  acid  or  alkalies,  oxygen,  nitrates,  par- 
ticularly potassium  and  ammonium  nitrates,  chlorids,  and 
sulfates. 

Non-corrosive  and  preventing  corrosion  by  the  above: 
Calcium  carbonate,  sodium  acid  carbonate,  ammonium 
carbonate,  calcium  silicate,  silica,  and  soluble  phosphates. 

TECHNIC  APPLICATIONS. 

Boiler  Waters. — The  main  conditions  affecting  the 
value  of  a  water  for  steam-making  purposes  are  its  tendency 
to  cause  corrosion  and  the  formation  of  scale.  Corrosion 
may  be  due  to  the  water  itself,  to  the  presence  of  free  acids, 
or  to  substances  which  form  acids  under  the  influence  of 
the  heat  to  which  the  water  is  subjected.  Pure  water — 
e.  g.,  distilled  water — exhibits  a  powerfully  corrosive  action 


120  INTERPRETATION  OF  RESULTS. 

upon  iron.  The  dissolved  oxygen  which  all  waters  contain 
also  aids  in  the  corrosion,  and  especially  when  accom- 
panied, as  is  usually  the  case,  by  carbonic  acid.  There 
is  always  greater  rusting  at  the  point  at  which  the  water 
enters  the  boiler,  since  there  the  gases  are  driven  out  of 
solution  and  immediately  attack  the  metal.  This  is  an 
evil  that  obtains  with  all  waters,  and  it  is  not  customary, 
in  making  examination  for  technic  purposes,  to  deter- 
mine the  amount  of  these  bodies.  In  water  that  has  had 
free  access  to  air,  the  oxygen  in  solution  is  a  tolerably  con- 
stant quantity,  and  it  is  sufficient  to  note  the  temperature 
and  refer  to  the  table  of  amounts  of  oxygen  dissolved  in 
water.  The  corrosive  action  of  oxygen  and  carbonic  acid 
is  especially  noticeable  in  waters  that  are  comparatively 
pure,  such  as  those  derived  from  mountain  springs.  This 
was  repeatedly  observed  by  Dr.  William  Beam,  in  the 
examination  of  the  waters  used  for  the  locomotives  of  the 
Baltimore  and  Ohio  Railroad.  The  waters  which  caused 
the  most  corrosion  were  mainly  those  containing  small 
quantities  of  solid  matter,  the  full  amount  of  oxygen,  and 
considerable  carbonic  acid,  but  no  other  acid  ot\  acid- 
forming  body. 

Free  acid,  other  than  carbonic  acid,  is  not  often  found 
in  water,  and  if  present,  renders  the  water  unfit  for  use, 
unless  it  be  neutralized.  Mine  waters  are  the  most  likely 
to  contain  free  acid,  sulfuric  acid  being  generally  present. 
Sometimes  the  acidity  is  due  to  organic  acids.  These 
act  very  injuriously  on  iron.  Allen  gives  an  example 
of  this  in  the  water  supplied  to  Sheffield,  England,  which 
he  found  to  contain  an  organic  acid  in  amount  equivalent 
to  from  3.5  to  10  parts  of  sulfuric  acid  per  million. 


TECHNIC   APPLICATIONS.  121 

Magnesium  chlorid  is  frequently  present  in  waters,  and 
if  in  considerable  quantity  may  be  very  harmful.  At  a 
temperature  of  310°  F.,  corresponding  to  an  effective 
pressure  of  four  atmospheres,  magnesium  •  chlorid  reacts 
with  water  to  form  magnesium  oxid  and  hydrochloric  acid, 
the  latter  attacking  the  boiler,  especially  at  the  water-line. 
If  there  be  present  at  the  same  time  considerable  calcium 
carbonate,  the  evil  may  be  somewhat  lessened,  but,  as  Allen 
has  pointed  out,  and  as  we  also  have  noticed,  there  may 
still  be  corrosion,  so  that  the  presence  of  more  than  a  small 
quantity  of  the  salt,  say  a  grain  or  two  to  the  gallon,  may 
be  considered  objectionable.  Allen  remarks  that  the 
presence  of  a  certain  amount  of  sodium  chlorid  may  pre- 
vent this  decomposition,  the  two  chlorids  combining  to 
form  a  stable  double  salt.  The  addition,  therefore,  of 
common  salt  to  a  water  containing  magnesium  chlorid  may 
act  to  diminish  corrosion,  a  point  which  will  bear  further 
investigation. 

It  has  not  been  determined  how  far  the  presence  of 
nitrites,  nitrates,  and  ammonia  affects  the  quality  of  water 
for  steam-making  purposes;  but  it  is  more  than  probable 
that  they  act  harmfully,  especially  the  nitrates,  which  are 
frequently  present  in  large  amount. 

Scale  is  composed  of  matters  deposited  from  the  water 
either  by  the  decompositions  induced  by  the  heat  or  by 
concentration.  When  the  deposit  is  loose,  it  is  termed 
sludge  or  mud,  and  usually  consists  of  calcium  carbonate, 
magnesium  oxid,  and  a  small  amount  of  magnesium  car- 
bonate. The  magnesium  oxid  is  formed  by  the  decompo- 
sition of  the  magnesium  carbonate  and  chlorid. 

The  formation  of  sludge  is  the  least  objectionable  effect, 


122  INTERPRETATION  OF  RESULTS. 

since  it  may  readily  be  removed  by  "blowing  off,"  pro- 
vided that  care  is  previously  taken  to  allow  the  flues  to 
cool  down  so  that  when  the  water  is  removed  the  heat  of 
the  flues  may  not  bake  the  deposit  to  a  hard  mass.  Waters 
containing  calcium  sulfate  form  hard  incrustations  difficult 
to  remove  and  causing  great  loss  of  fuel  by  interfering 
with  the  transmission  of  the  heat  to  the  water.  It  not 
only  forms  a  hard  incrustation  in  itself,  but  becomes  in- 
corporated with  the  mud,  and  renders  it  also  hard.  The 
hard  scale  will  also  contain  practically  all  the  silica  and 
the  iron  and  aluminum  present  in  the  water,  besides  any 
matters  originally  held  in  suspension. 

It  follows  from  the  above  that  a  water  only  temporarily 
hard  will,  if  care  is  taken  in  the  management  of  the  boiler, 
cause  the  formation  merely  of  a  loose  deposit  of  sludge — 
temporary  hardness  being  due  in  the  main  to  calcium  and 
magnesium  carbonates.  A  water  permanently  hard  will 
probably  form  a  hard  scale,  since  such  hardness  is  usually 
due  to  calcium  sulfate. 

In  accordance  with  these  principles,  the  analysis  of  a 
water  for  steam-making  purposes  may  include  the  deter- 
minations of  free  acid,  total  solid  residue,  SO4,  Cl,  Ca,  Mg, 
temporary  and  permanent  hardness.  In  cases  in  which 
the  qualitative  tests  show  but  small  amounts  of  SO4  and 
Cl,  the  analysis  may  be  limited  to  the  determinations  of 
the  temporary  and  permanent  hardness. 

In  the  laboratory  of  the  Pennsylvania  Railroad  an  ap- 
proximate determination  of  scale-forming  ingredients  is 
made  in  the  following  manner:  The  total  solids  obtained 
by  evaporation  are  treated  with  diluted  alcohol  (fifty  per 


TECHNIC   APPLICATIONS.  123 

cent.),  and  the  undissolved  residue  is  denominated  "scale- 
forming  material." 

It  has  been  pointed  out  in  an  earlier  chapter  that  it  is 
not  possible  to  deduce  from  the  analytic  result  the  exact 
forms  in  which  the  various  elements  are  combined,  but 
since  it  is  known  that  at  the  high  temperature  ordinarily 
reached  in  boilers  definite  chemical  changes  occur,  it  is 
safest  to  exhibit  the  maximum  amount  of  corrosive  and 
scale-forming  ingredients  which  the  water  under  these  cir- 
cumstances could  develop.  Thus,  since  calcium  sulfate 
is  practically  insoluble  in  water  above  212°  F.,  the  pro- 
portion of  calcium  sulfate  may  be  regarded  as  such  as 
would  be  formed  by  the  total  quantity  of  calcium  or  the 
total  quantity  of  SO4,  according  to  which  is  present  in  the 
larger  amount.  Similarly,  as  the  decomposition  of  magne- 
sium chlorid  is  induced  by  the  high  temperature  of  the 
boiler,  the  analytic  statement  should  indicate  the  maxi- 
mum proportion  of  this  compound  obtainable  from  the 
magnesium  and  chlorin  present.  These  rules  can  not  apply 
absolutely  to  waters  rich  in  alkali  carbonates,  since  these 
would  neutralize  any  acid  formed  from  the  magnesium 
chlorid,  or  even  prevent  its  formation,  and  would  prevent, 
to  a  large  extent,  the  formation  of  calcium  sulfate.  Much 
remains  to  be  determined  concerning  the  effects  of  the 
high  temperature  and  concentration  to  which  boiler  waters 
are  subjected. 

General  Technic  Uses.— In  regard  to  the  quality 
of  water  for  technic  other  than  steam-making  purposes, 
such  as  brewing,  dyeing,  tanning,  etc.,  no  detailed  methods 
or  standards  can  be  laid  down.  The  nearest  approach 
to  purity  that  can  be  secured  in  the  supply  will  be  of  the 


124          INTERPRETATION  OF  RESULTS. 

greatest  advantage.  The  more  objectionable  qualities  will 
be  large  proportion  of  organic  matter,  especially  if  it  dis- 
tinctly colors  the  water,  excessive  hardness,  and  notable 
amounts  of  iron  or  free  mineral  acid.  It  is  said  that  one 
part  of  iron  per  million  will  render  water  unsuitable  for 
bleaching  establishments.  It  has  been  noted  that  a  large 
proportion  of  active  microbes  is  injurious  in  the  manufac- 
ture of  indigo.  In  artificial  ice  making,  a  very  pure  water 
must  be  used  if  a  clear  and  colorless  product  be  desired. 
Any  suspended  or  dissolved  coloring-matter  will  be  con- 
centrated by  the  freezing  and  appear  in  the  bottom  or 
center  of  the  mass. 

The  examination  of  sewage-effluents  and  waste  waters 
from  manufacturing  establishments  is  to  be  conducted 
upon  the  same  principles  as  for  ordinary  supplies,  but 
especial  attention  must  be  given  to  the  presence  of  poison- 
ous metals  and  free  mineral  acids.  The  latter  interfere 
with  the  normal  self-purification  of  the  water.  For  the 
nitrogen  determination,  the  Kjeldahl  process  will  be  found 
more  satisfactory  than  that  by  alkaline  permanganate. 

PURIFICATION  OF  DRINKING  WATER. 
The  most  obvious  method  of  purifying  water  is  by  dis- 
tillation. The  process  is  too  expensive  for  general  use, 
but  is  especially  adapted  for  water  intended  for  pharma- 
ceutic  or  analytic  purposes.  It  has  also  been  used  for 
supplying  vessels  at  sea  and  in  tropic  localities  in  which 
the  natural  waters  may  be  contaminated  with  malarial  or 
other  germs.  The  majority  of  microbes  are  killed  by 
short  exposure  to  a  temperature  of  212°  F. ;  hence,  water 
may  be  purified,  on  a  small  scale,  by  simple  boiling.  Freez- 


PURIFICATION   OF   DRINKING   WATER. 


125 


ing  does  not  have  as  beneficial  an  effect,  many  microbes 
retaining  vitality  for  a  long  time  in  ice,  and  even  at  very 
low  temperatures. 


FIG.  14. 


For  the  rapid  sterilization  of  water^the  Forbes  sterilizer 
is  useful.     Its  efficiency  has  been  ascertained.     The  in- 


126  INTERPRETATION  OF  RESULTS. 

ternal  construction  is  shown  in  figure  14.  It  is  so  arranged 
that  the  incoming  water  is  kept  in  lively  boiling  by  which 
it  constantly  overflows  into  the  cooling  tube,  and,  in  de- 
scending this,  imparts  its  heat  to  the  incoming  current,  thus 
securing  a  heat-exchange  which  makes  the  operation 
economic.  The  water  is  not  distilled  nor  filtered,  but 
pathogenic  microbes  are  killed.  The  illustration  shows 
a  form  intended  for  detached  use,  but  arrangements  are 
also  available  for  operation  in  connection  with  a  constant 
supply. 

The  self-purification  of  water — that  is,  the  destruction  of 
organic  matter  and  pathogenic  microbes,  by  reason  of  the 
development  of  the  ordinary  microbes  of  putrefaction — 
occurs  satisfactorily  only  in  alkaline  waters,  hence,  acid 
effluents  check  this  process.  The  addition  of  lime  in  suffi- 
cient amount  to  give  a  slightly  alkaline  reaction  will  be 
beneficial. 

The  conditions  necessary  to  secure  self-purification  of 
surface  waters  are  not  fully  understood,  and  it  is  unsafe  to 
state  that  a  polluted  stream  will  purify  itself  in  any  given 
distance.  It  must  also  be  remembered  that  the  dilution 
of  infected  sewage  by  its  introduction  into  a  large  volume 
of  uninfected  water  will  assist,  for  a  time  at  least,  the 
multiplication  of  pathogenic  microbes. 

The  methods  in  general  use  for  purifying  water  are 
simple  filtration  and  the  removal  of  the  impurities  by  ap- 
propriate chemical  agents. 

Filtration. — For  household  purposes  forms  of  carbon, 
stone,  and  sand  filters  are  used,  which  yield  clear  filtrates, 
but  permit,  sooner  or  later,  the  transmission  of  microbes. 
The  suspended  matter  in  the  water  gradually  accumulates 


PURIFICATION   OF   DRINKING   WATER.  127 

on  the  surface  of  the  filter,  and  causes  a  great  increase  in 
the  number  of  the  microbes,  some  species  of  which  appar- 
ently grow  through  the  pores  of  the  filter,  and  are  carried 
into  the  filtrate.  The  following  are  among  the  more 
efficient  forms  of  household  filters: 

Chamberlain- Pasteur  Filter. — This  consists  of  tubes  of 
unglazed  biscuit-ware,  the  number  depending  on  the 
size  and  required  delivery  of  the  filter.  There  are  arrange- 
ments for  continuous  filtration  by  attaching  the  tube  to 
the  faucet;  also  forms  adapted  to  simultaneous  cooling  and 
filtration.  The  observations  of  Pasteur  and  others  have 
shown  that  this  is  a  highly  efficient  filter,  yielding  for  a  con- 
siderable time  a  filtrate  entirely  sterile.  It  requires  oc- 
casional cleaning,  since,  after  continuous  use,  the  microbes 
may  pass  through  the  pores,  probably  by  a  process  of 
growth.  An  occasional  boiling  of  the  tubes  in  water  would 
be  sufficient  to  overcome  this  difficulty.  The  Berkefeld 
filter  is  of  this  type. 

Many  other  forms  of  filters  have  been  devised.  Com- 
prehensive comparative  tests  show  that,  except  as  to  those 
based  on  the  principle  of  the  Chamberlain-Pasteur  filter, 
but  little  time  elapses  before  the  filtrate  contains  numerous 
microbes. 

For  the  purification  of  water  on  the  large  scale  the  value 
of  sand  filters  has  been  so  thoroughly  established  that  the 
method  needs  no  further  discussion.  The  construction 
and  operation  of  these  filters  are  engineering  questions 
entirely. 

Precipitation  Methods. — A  small  quantity  of  aluminum 
sulfate  added  to  natural  waters  is  decomposed  with  the 
formation  of  a  flocculent  precipitate  of  aluminum  hydroxid, 


128          INTERPRETATION  OF  RESULTS. 

which  settles  comparatively  rapidly,  and  carries  down  with 
it  all  suspended  matters,  as  well  as  a  large  proportion  of  the 
dissolved  organic  matters.  Waters  which  contain  such  an 
excess  of  organic  matter  as  to  be  distinctly  colored  may 
usually  be  made  quite  clear  and  colorless  by  this  treatment. 
One  grain  to  the  gallon  will  often  suffice  for  the  purpose, 
but  if  very  rapid  subsidence  is  desired,  more  may  be  added. 

This  precipitation  is  a  gradual  process,  and  a  water  that 
will  give  the  test  for  aluminum  immediately  after  filtering 
may  give  none  after  twenty-four  hours.  It  is  not  infre- 
quently noted  that  such  effluents,  originally  clear,  become 
cloudy  on  standing,  in  consequence  of  the  separation  of 
aluminum  hydroxid.  On  the  addition  of  aluminum  sul- 
fate  to  brown  surface  waters  there  is  also  a  precipitation 
by  the  organic  matters.  A  sample  of  the  Cochituate  River 
water  (Boston  supply),  of  moderately  deep  color,  to  which 
25  milligrams  of  alum  to  the  liter  had  been  added,  when 
filtered  gave  no  reaction,  even  when  2.5  liters  were  con- 
centrated for  the  test.  An  addition  of  30  milligrams  to 
the  liter  could  be  detected  without  difficulty. 

Several  systems  of  filtration  now  in  extended  use  employ 
this  precipitation  method  in  conjunction  with  filters  of 
small  area,  the  necessary  flow  being  obtained  by  increased 
pressure.  The  differences  between  the  various  forms  are 
chiefly  in  the  mechanical  arrangements  for  supplying  the 
water  and  for  cleaning  the  filter.  The  material  is  generally 
sand  or  coke;  the  cleaning  is  performed  at  short  intervals, 
by  means  of  reverse  currents  of  water.  The  aluminum 
solution  is  introduced  as  needed  by  automatic  apparatus. 

These  filters  are  efficient,  and  are  suitable  for  the  purifi- 
cation of  water  for  manufacturing  establishments,  and  when 


PURIFICATION   OF   DRINKING   WATER.  129 

large  basins  are  not  available.  It  must  be  noted,  how- 
ever, that  the  use  of  aluminum  sulfate  will  increase  the 
liability  of  the  water  to  form  hard  scale.  This  can  be 
avoided  by  using  some  other  aluminum  salt. 

The  addition  of  an  iron  salt  to  water  containing  carbon- 
ates is  attended  with  decomposition  and  the  formation  of 
a  precipitate  of  ferric  hydroxid.  This  reaction  has  been 
employed  as  a  means  of  purification.  One  of  these  meth- 
ods was  by  passing  the  water  through  spongy  iron,  then 
aerating  to  precipitate  the  iron,  and  filtering  through  sand. 
The  method  is  very  efficient,  but  the  spongy  iron  gradu- 
ally chokes  by  oxidation  and  becomes  useless.  This  diffi- 
culty is  removed  by  the  use  of  iron  borings  or  pun  chin  gs 
contained  in  an  iron  cylinder,  which  is  rotated  while  the 
water  passes  through;  the  iron  is  brought  into  thorough 
contact  with  the  water,  and  there  is  sufficient  abrasion  to 
keep  its  surface  clean. 

In  the  laboratory  of  the  State  Board  of  Health  of  Mass- 
achusetts, Drown  investigated  the  effect  of  various  methods 
of  aeration,  such  as  exposing  water  in  bottles  to  the  air 
of  the  room,  drawing  a  current  of  air  through  by  means 
of  an  aspirator,  shaking  it  in  a  bottle  by  machinery,  and 
exposing  it  to  air  under  pressure  of  from  sixty  to  seventy- 
five  pounds.  While  no  appreciable  benefit  so  far  as  re- 
gards the  organic  matter  and  its  decomposition-products 
occurs,  aeration  appears  to  prevent  the  growth  of  alg«, 
with  the  troublesome  accompaniments  of  bad  tastes  and 
odors.  It  may  also  have  a  beneficial  effect  upon  ground 
waters  containing  considerable  amounts  of  iron.  These 
waters  are  often  clear  when  first  drawn,  but  become  turbid 
i 


130          INTERPRETATION  OF  RESULTS. 

and  yellow  in  a  few  hours  by  the  separation  of  ferric  hy- 
droxid  by  oxidation.  Waters  from  considerable  depth 
often  contain  so  little  free  oxygen  that  this  oxidation  does 
not  occur  until  they  reach  the  surface.  By  applying  an 
aeration  method  the  change  may  be  hastened,  and  by  some 
simple  process  of  rapid  nitration  afterward  applied,  the 
water  will  be  made  clear  and  remain  so. 

Filtration  through  bone  charcoal,  which  contains  con- 
siderable calcium  phosphate,  will  remove  small  amounts 
of  lead,  copper,  and  arsenic. 

Purification  of  Boiler  Waters. — The  problems  present 
in  the  treatment  of  boiler  waters  are  usually  the  removal 
of  the  calcium  carbonate  and  sulfate,  and  magnesium 
carbonate  and  chlorid.  Both  carbonates  are  appreciably 
soluble  in  pure  water.  About  one  grain  of  calcium  car- 
bonate to  the  gallon  is  usually  stated  to  be  the  proportion 
dissolved,  but  it  has  been  pointed  out  by  Allen  that  solu- 
tions can  be  obtained  containing  twice  this  amount.  If 
the  water  contains  carbonic  acid,  it  will  take  up  a  much 
greater  proportion  of  the  carbonates,  but  in  this  case  they 
will  be  deposited  from  the  solution  by  boiling.  This  has 
been  accounted  for  by  supposing  the  existence  of  soluble 
bicarbonates,  which  are  decomposed_by  the  boiling.  Nearly 
all  of  these  carbonates  can  be  thrown  out  of  solution  by 
any  means  that  will  deprive  the  water  of  the  carbonic  acid. 
Sodium  hydroxid  is  often  employed  for  the  purpose,  and 
should  be  added  in  quantity  just  sufficient  to  form  normal 
sodium  carbonate.  If  there  are  present  in  the  water 
calcium  and  magnesium  chlorids  and  sulfates,  these  also 
will  be  decomposed  and  precipitated  by  the  sodium  car- 


PURIFICATION   OF  DRINKING   WATER.  131 

bonate  so  formed.  If  the  amount  of  sodium  carbonate 
formed  is  not  sufficient  to  decompose  all  of  these  bodies,  a 
sufficient  quantity  should  be  added  with  the  sodium  hy- 
droxid  to  effect  the  complete  decomposition.  The  pre- 
cipitate is  allowed  to  settle  or  filtered  off. 

In  cases  in  which  the  feed-water  is  heated  before  it  enters 
the  boiler,  it  may  only  be  necessary  to  add  to  the  water 
sodium  carbonate  in  quantity  sufficient  to  decompose  the 
calcium  and  magnesium  chlorids  and  sulfates,  since  the 
heat  alone  will  suffice  to  throw  down  the  carbonates. 

Care  should  be  taken  in  these  precipitations  that  no 
more  sodium  hydroxid  is  added  than  is  required  for  the 
precipitation,  since  any  excess  would  tend  to  corrode  the 
boiler. 

Clark's  process  consists  in  treating  the  water  with  calcium 
hydroxid  (lime-water).  This  precipitates  the  calcium  and 
magnesium  carbonates  by  depriving  the  water  of  its  free 
carbonic  acid.  It  has,  of  course,  no  effect  upon  the  cal- 
cium sulfate.  It  is  to  be  noted  that  the  proportion  of 
calcium  hydroxid  which  is  to  be  added  must  be  calculated 
from  the  amount  of  free  carbonic  acid  existing  in  the  water, 
and  not  from  the  amount  of  carbonates  to  be  removed. 
The  precipitate  will  usually  require  at  least  twelve  hours 
for  complete  subsidence,  but  after  three  or  four  hours  the 
water  will  be  sufficiently  clear  for  some  purposes.  If  a 
filter  press  is  used,  as  in  Porter's  process,  the  time  required 
for  clarification  is  very  much  shortened.  Another  advan- 
tage of  this  process  is  the  use  of  a  solution  of  silver  nitrate, 
in  order  to  determine  more  conveniently  the  proportion 
of  calcium  hydroxid  which  is  to  be  employed.  The  lime 
is  first  slaked  and  dissolved  in  water,  and  the  water  to  be 


132  INTERPRETATION  OF  RESULTS. 

softened  run  in  and  thoroughly  mixed  with  it.  From  time 
to  time  small  portions  are  taken  out  and  a  few  drops  of  a 
solution  of  silver  nitrate  added.  As  long  as  the  lime  is  in 
excess,  a  brownish  coloration  is  produced.  When  this  has 
become  quite  faint,  and  just  about  to  disappear,  the  addi- 
tion of  the  water  is  discontinued,  and,  after  a  short  time, 
the  water  is  filtered  by  means  of  the  press. 

Soluble  phosphates  added  to  a  water  precipitate  com- 
pletely in  a  flocculent  condition  any  calcium,  magnesium, 
iron,  or  aluminum.  This  reaction  can  be  best  applied  by 
using  the  trisodium  phosphate  (Na3PO4-[~  i2H8O),  which 
is  now  a  commercial  article.  By  reason  of  the  facility  with 
which  this  substance  loses  a  portion  of  its  sodium  to  acids, 
it  acts  not  only  as  a  precipitant  to  the  above  materials,  but 
will  neutralize  any  free  mineral  acid  present  in  the  water. 
From  evidence  submitted  by  those  who  have  used  the  pro- 
cess on  the  large  scale,  it  appears  that  not  only  is  no  hard 
scale  formed,  but  that  scale  already  existing  prior  to  its 
use  is  gradually  disintegrated  and  removed  with  the  sludge. 
Experiments  indicate  that  no  injury  results  from  an  excess 
of  the  material;  but  the  economical  employment  of  the 
method,  especially  with  very  hard  waters,  can  only  be 
based  upon  a  correct  analysis,  and  an  estimation  of  the 
phosphate  required  for  the  precipitation.  In  many  cases 
the  composition  of  the  water  will  be  such  that  a  partial 
precipitation  will  be  sufficient. 

Considerable  success  has  been  obtained  by  the  use  of 
fluorids  as  precipitants  of  scale-forming  elements.  Sodium 
aluminate  has  also  been  recommended. 

Waters  rich  in  ferrous  compounds  may  be  purified  by 


IDENTIFICATION   OF   THE   SOURCE   OF   WATER.          133 

thorough  aeration  and  nitration,  the  iron  being  separated 
as  ferric  hydroxid. 

The  corrosive  action  of  very  pure  waters  is  partially 
abated  by  filtration  through  bone  charcoal  or  by  addition 
of  small  amounts  of  lime. 

IDENTIFICATION  OF  THE  SOURCE  OF  WATER. 

The  determination  of  the  course  of  underground  streams, 
and  of  communications  between  collections  of  water,  is 
often  an  important  practical  problem.  In  geologic  and 
sanitary  surveys,  valuable  information  may  occasionally  be 
gained.  The  method  generally  pursued  when  connection 
between  water  at  accessible  points  is  to  be  detected,  is  to 
introduce  at  one  point  some  substance  not  naturally  exist- 
ing in  the  water,  and  capable  of  recognition  in  small  amount. 
Lithium  compounds  are  among  the  best  for  this  purpose. 
They  are  not  frequent  fngredients  of  natural  waters,  and 
are  easily  recognized  by  the  spectroscope.  Lithium  chlorid 
is  the  most  suitable.  The  quantity  to  be  employed  will 
vary  with  circumstances.  It  scarcely  needs  to  be  stated 
that  the  waters  under  examination  should  be  carefully 
tested  for  lithium  before  using  the  method. 

When  the  lithium  method  is  inadmissible,  recourse  must 
be  had  to  other  substances  of  distinct  character,  such  as 
strontium  chlorid,  but  this  possesses  the  disadvantage  that 
a  considerable  amount  may  be  rendered  insoluble,  and 
thus  lost  in  the  ordinary  transit  through  soil.  Use  has 
been  made  of  organic  coloring  matters  of  high  tinctorial 
power,  one  of  the  most  suitable  of  which  is  fluoresce'in, 
C20H12O5,  a  derivative  of  benzene.  This  will  communi- 
cate a  characteristic  and  intense  fluorescence  to  many 


134  INTERPRETATION  OF  RESULTS. 

thousand  times  its  weight  of  water.  The  coloration  is 
distinct  only  in  alkaline  liquids.  Other  colors,  such  as 
anilin-red,  may  be  employed. 

I  am  indebted  to  Dr.  F.  P.  Vandenburgh,  who  conducted 
the  investigation,  for  a  description  of  an  instance  of  the 
application  of  the  above  methods.  In  a  suit  at  law  grow- 
ing out  of  use  of  a  creek  for  the  supply  of  Syracuse,  N.  Y., 
it  was  alleged  that  the  creek  supplied  a  spring  which  was 
used  by  a  manufacturing  establishment.  Tests  of  the 
water  of  creek  and  spring  for  lithium  were  made,  ten  gallons 
of  each  being  evaporated,  with  negative  results.  Twenty- 
five  pounds  of  lithium  carbonate  were  converted  into 
chlorid  and  poured  into  the  stream  about  half  a  mile  from 
the  spring.  Samples  of  ten  gallons  each  were  taken  out  of 
the  spring  by  almost  continual  dipping  during  forty-eight 
hours  following.  Twenty  of  these  samples  were  examined 
and  lithium  found  in  each. 

Ten  pounds  of  fluorescem  were  introduced  at  a  point 
about  one  mile  above  the  spring,  and  the  characteristic 
fluorescence  appeared  at  the  spring  about  six  hours  after 
its  introduction  into  the  creek.  The  greatest  intensity  of 
color  was  between  six  and  ten  hours  after  its  introduction. 

A  more  important  feature  of  the  problem  from  a  sanitary 
point  of  view  is  the  determination  of  the  source  of  a  given 
current  or  collection  of  water,  when  such  source  is  in- 
accessible. Problems  of  this  character  are  not  infrequent 
in  large  cities  in  which  the  systems  of  water-supply  and 
drainage  are  defective,  thus  giving  occasion  to  accumu- 
lations of  water  in  cellars  and  similar  places.  Often,  in 
these  cases,  no  extended  explorations  can  be  made,  by 
reason  of  the  adjacent  buildings  and  conflicting  property 


IDENTIFICATION    OF    THE    SOURCE    OF    WATER.          135 

interests,  and  the  question  may  arise  whether  the  water 
proceeds  from  a  leaky  hydrant,  drain,  sewer,  or  subsoil 
current.  It  is  obvious  that  in  the  case  of  the  collection 
of  water  in  a  cellar  from  causes  other  than  surface  washings 
or  entrance  of  rain,  it  must  have  passed  through  some 
distance  of  soil,  and  in  built-up  districts  will  almost  certainly 
be  charged  with  organic  refuse.  To  correctly  interpret 
the  results,  it  will  be  necessary  to  know  the  general  char- 
acter of  the  subsoil  water  of  the  district  and  the  composition 
of  the  public  supply.  As  a  rule,  the  transmission  of  water 
through  moderate  distances  of  soil  will  not  materially  in- 
crease the  mineral  constituents.  Hence,  if  the  sample  con- 
tains an  excess  of  dissolved  matters  as  compared  with  the 
water-supply  of  the  district,  it  may  reasonably  be  inferred 
that  it  is  derived  from  a  drain,  sewer,  or  subsoil  current. 
In  these  investigations  it  will  generally  be  sufficient  to  deter- 
mine the  total  solids,  odor  on  heating,  chlorin,.nitrates,  and 
nitrites. 

Occasionally,  the  analytic  results  will  be  ambiguous,  and 
it  is  advisable  to  make  examinations  of  more  than  one 
sample,  since  accidental  circumstances,  rain-fall,  etc.,  may 
affect  the  composition  of  the  water. 

Instances  of  the  contamination  of  water  by  unusual  sub- 
stances are  occasionally  noted,  and  these  sometimes  afford 
a  clue  to  the  source  of  the  water.  Among  the  instances 
of  this  kind  within  my  own  experience  may  be  noted  the 
contamination  with  petroleum  and  with  soap.  In  the 
former  case  it  was  evident  that  the  contamination  was  from 
a  leaky  pipe  connecting  two  refineries.  In  the  latter  it 
was  shown  to  be  derived  from  an  adjoining  building  used 
as  a  laundry. 


136  ANALYTIC   DATA. 


DATA   FOR   CALCULATION. 

Parts  per      100,000       X  0.7  =  Grains  per  Imperial  Gallon. 

"     1,000,000       X  0-07         =        "          "  "  " 

100,000       X  0.583  "         "    U.  S. 

"     1,000,000       X  0.058 

;     1,000,000       X  0.00833  =  Pounds  per  1000  U.  S.  Gal. 

Grains"     Imp.  gallon  -=-  0.7  =  Parts  per      100,000 

-j-   0.07  "         "     1,000,000 

"       "     U.  S.    "        -*-  0.583  "         "        100,000 

-*-'  0.058  "         "     1,000,000 

A1203, Xo.53    =A1 

AgCl, X  0.247  =  C1 

BaSO4, X  0.588  =  Ba 

BaS04, X  0.411  =  S04 

BaS04, X  0.342  =  S03 

B203, X  0.314  =  B 

CaO, X  0.714  =  Ca 

CaO, X  1-78    =  CaCO3 

'  CaC03, X  0.40    =  Ca 

Cl, X  1-65    :=  NaCl 

Fe203, Xo.7       =Fe 

KC1, X  0.524  =  K 

2KC1,  PtCl4, X  0.16    =  K 

2KC1,  PtCl4,____  X  0.307  =  KC1 

Mg2P207, X  0.218  =  Mg 

Mg2P207, X  0.853  =  P04 

Mg2P207, X  0.757  =  MgC03 

MnS, X  0.633  =  Mn 

NaCl, X  0.394  =  Na 

N, X  4-42    =  N03 

N, X3-27    -=N02 

N, X  5-84    ==  Ca(N03)2 

N, X  i.2i    =NH3 

NH3, X  0.823  =  N 


ANALYTIC   DATA. 


CONVERSION  TABLE. 


PARTS 

PER 

MILLION. 

GRAINS  PER 
U.S.  GALLON. 

GRAINS 

PER 

IMP.  GAL. 

PARTS 

PER 

MILLION. 

GRAINS  PER 
U.S.  GALLON. 

GRAINS 

PER 

IMP.  GAL. 

I 

0.058 

0.07 

26 

I.S08 

1.82 

2 

0.116 

0.14 

27 

1.566 

1.89 

3 

0.174 

0.21 

28 

1.624 

1.96 

4 

0.232 

0.28 

29 

1.682 

2.03 

5 

0.290 

0-35 

3° 

1.740 

2.10 

6 

0.348 

0.42 

31 

1.798 

2.17 

7 

0.406 

0.49 

32 

1.856 

2.24 

8 

0.464 

0.56 

33 

1.914 

2.31 

9 

0.522 

0.63 

34 

1.972 

2.38 

10 

0.580 

0.70 

35 

2.030  - 

2-45 

ii 

0.638 

0.77 

36 

2.088 

2.52 

12 

0.696 

0.84 

37 

2.146 

2-59 

13 

°-754 

o«pi 

38 

2.204 

2.66 

14 

0.812 

0.98 

39 

2.262 

2-73 

15 

0.870 

1.05 

40 

2.320 

2.80 

16 

0.928 

1.  12 

4i 

2.378 

2.87 

17 

0.986 

I.I9 

42 

2.436 

2-94 

18 

1.044 

1.26 

43 

2-494 

3.01 

19 

I.IO2 

J-33 

44 

2-552 

3.08 

20 

1.  1  60 

1.40 

45 

2.610 

3-i5 

21 

1.218 

•47 

46 

2.668 

3-22 

22 

1.276 

•54 

47 

2.726 

3-29 

23 

1-334 

.61 

48 

2.784 

3^36 

24 

1.392 

.68 

49 

2.842 

3-43 

25 

1.450 

•75 

5° 

2.900 

3-5° 

INDEX. 


A  CIDS,  action  on  lead,  117 
•"•     Actinic  method  for  organic   mat- 
ter, 59 

Action  of  water  on  lead,  117 
Aeration  of  water,  116,  129 
Agar,  78 

Albuminoid  ammonia,  44,  112 
Alkali  carbonates,  determination  of,  97 
Alkaline  permanganate,  42 
Alum,  action  of,  127 

,  test  for,  67 

,  use  of,  127 

Aluminum,  determination  of,  88 

,  test  for,  67 

Ammonia,  albuminoid,  44,  112 

,  free,  43,  in 

free  water,  41 

process,  34 

Ammonium  chlorid,  standard,  41   .' 

molybdate,  60 

Analysis,  statement  of,  106 
Analytic  operations,  22 
Arsenic,  detection  of,  64 
Artesian  water,  16,  116 


OACILLUS  typhosus,  87 

coli  communis,  87 

Bacteriologic  examination,  74 
Barium,  detection  of,  63 
Biologic  examination,  69 
Boiler  scale,  102,  121 

water,  119 

— ,  purification  of ,  119 
Boric  acid  estimation,  102 
Bouillon,  77 


compounds,  removal  of, 

,  determination  of,  88 
sulfate  in  boiler  water,  123 
,  insolubility  of,  123 


-  ,  determination  of  normal,  95 
Carbonic  acid,  determination  of,  100 
Chlorin,  determination  of,  32 

-  ,  significance  of,  1  10 
Chromium,  detection  of,  63 


Clarifying  water,  24,  126 
Clark's  process,  131 
Collection  of  samples,  22 
Color  comparator,  46 

,  determination  of,  25 

,  significance  of,  108 

Comparison  cylinders,  46 
Conversion  of  ratios,  136,  137 
Copper,  detection  of,  68 

zinc  couple,  52 

Corrosion  of  boilers,  119 
Cultivation  of  microbes,  81,  116 
Culture-media,  76 


"P\EEP  water,  16,  116 

•*•'     Demijohn  for  water  samples,  22 

Denitrification,  19 

Distilling  apparatus,  34 


•pERRIC  sulfate,  standard,  34 
•*•       Ferrous  ammonium  sulfate,  stan- 
dard, 6 1 

Filters,  71,  72,  126 
Filtration,  127 
Fluorescein,  use  of ,  134 
Forbes'  sterilizer,  125 


GALLON,  Imperial,  106 
— ,  U.  S.,  106 
Gelatin  culture-media,  76 
Ground  water,  16,  116 


TJARD  scale,  122 

•*• A     water,  softening  of,  130 

Hardness,  95,  116 

,  permanent,  96 

,  temporary,  97 

Hydrogen  sulfid,  titration  of,  94 


IDENTIFICATION 
x     water,  133 
Imperial  gallon,  106 
Indol  reaction,  84 


of     source     of 


139 


140 


INDEX. 


Interpretation  of  results,  106 

lodin,  centinormal,  94 

Iron,  action  of,  in  purification,  129 

,  determination  of,  65,  88 

,  significance  of,  1 10 


T   EAD,  action  of  water  on,  117 

•*•"'     — • determination  of,  68 

Lithium  compounds,  use  of,  127 

,  detection  of,  103 

— ,  separation  of,  93 
Litmus  agar,  81 


TV/TAGNESIA  in  boiler  sludge,  121 
•*•"•  Magnesium,  determination  of, 
chlorid,  effects  of,  121 


Manganese,  detection  of,  66 
—  ,  determination  of,  90 
Microbes  of  water,  83 
Micro-filter,  72 


TyjESSLER  reagent,  41 
•*• '      Nesslerizing,  46 

— ,  determination  of,  50 

,  formation  of,  19 

,  significance  of,  114 

Nitrification,  19 

Nitrites,  determination  of,  53 

,  formation  of,  19 

— ,  significance  of,  114 
Nitrogen  in  ammonium,  44,  1 1 1 

—  as  nitrates,  50,  114 

—  as  nitrites,  53,  113 

—  by  permanganate,  44,  112 

,  oxidation  of,  19 

,  total  organic,  48,  113 


/"}DOR,  determination  of,  27 

^ from  residue,  31 

— ,  significance  of,  108 

— consuming  power,  55,  115 
,  dissolved,  61,  116 


OARIETTI'S  solution,  85 

•*•       Pasteur-Chamberlain  filter,  127 

Permanganate  method,  44 

standard,  56 

Petri  dish,  75 
Phenol  broth,  85 

—  disulfonic  acid,  5 1 

,  determination  of,  60 

,  significance  of,  no 

Potassium  chromate  solution,  32 


,  determination  of,  93 

iodid  solution,  57 

nitrate,  standard,  51 

permanganate,  alkaline,  42 

thiocyanate,  33 

Potato  culture,  80 
Pure  water,  corrosive  action  of,  119 
Purification  of  boiler  water,  130 
of  drinking  waters,  124 

"DAIN  water,  16,  116 

^     Ratios,  conversion  of ,  136,  137 
Reaction,  28 
Residue,  charring  of,  3 1 
Results,  statement  of,  106 
River  water,  16 


CAMPLES,  collection  of,  22 
°     Sand  filters,  127 
Sanitary  examinations,  22 
Scale,  102,  121 

,  analysis  of,  102 

Silica,  determination  of,  87 
Silver  nitrate,  standard,  32 

—  nitrite,  preparation  of,  54 

—  test  for  organic  matter,  59 
Sludge,  121 

Soap  solution,  98 

Sodium  and  potassium,  separation  of,  91 

,  carbonate  solution,  90 

,  determination  of,  92 

hydroxid  solution,  49 

nitrite,  standard,  54 

thiosulfate,  57 

Solids,  significance  of,  109 

,  total,  29 

Source  of  water,  tracing,  133 
Specific  gravity,  104 
Spectroscopic  examination,  103 
Spongy  iron  filter,  129 
Starch  indicator,  57 
Statement  of  analysis,  106 
Subsoil  water,  16,  116 
Sulfates,  determination  of,  90 
Sulfids,  20,  94 

,  determination  of,  94 

Surface  water,  16 


npECHNIC  examinations,  87 
A      Total  solids,  29 
Turbidity,  27 


,  detection  of,  64 


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